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 $93.34   3.517%   $96.6228   $96.62   $96.60   $96.60  
  Purchase #2 $155.57   7.725%   $167.5878   $167.59   $167.60   $167.60  
  Purchase #3 $166.41   7.722%   $179.2602   $179.26   $179.25   $179.30  
  Purchase #4 $245.65   9.711%   $269.5051   $269.51   $269.50   $269.50  
  Purchase #5 $195.80   6.196%   $207.9318   $207.93   $207.95   $207.90  
  Purchase #6 $106.58   10.668%   $117.95   $117.95   $117.95   $118.00  
  Purchase #7 $144.88   5.113%   $152.2877   $152.29   $152.30   $152.30  
  7 purchase totals = $1,108.23       $1,191.1454   $1,191.15   $1,191.15   $1,191.20