Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $177.38   5.566%   $187.253   $187.25   $187.25   $187.30  
  Purchase #2 $210.97   5.389%   $222.3392   $222.34   $222.35   $222.30  
  Purchase #3 $145.94   5.109%   $153.3961   $153.40   $153.40   $153.40  
  Purchase #4 $194.86   4.347%   $203.3306   $203.33   $203.35   $203.30  
  Purchase #5 $160.41   4.515%   $167.6525   $167.65   $167.65   $167.70  
  Purchase #6 $225.82   6.814%   $241.2074   $241.21   $241.20   $241.20  
  Purchase #7 $189.49   11.372%   $211.0388   $211.04   $211.05   $211.00  
  7 purchase totals = $1,304.87       $1,386.2176   $1,386.22   $1,386.25   $1,386.20