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 $191.61   5.807%   $202.7368   $202.74   $202.75   $202.70  
  Purchase #2 $10.82   6.485%   $11.5217   $11.52   $11.50   $11.50  
  Purchase #3 $203.62   5.384%   $214.5829   $214.58   $214.60   $214.60  
  Purchase #4 $243.33   12.410%   $273.5273   $273.53   $273.55   $273.50  
  Purchase #5 $63.99   7.154%   $68.5678   $68.57   $68.55   $68.60  
  Purchase #6 $109.71   9.526%   $120.161   $120.16   $120.15   $120.20  
  Purchase #7 $120.99   11.803%   $135.2704   $135.27   $135.25   $135.30  
  7 purchase totals = $944.07       $1,026.3679   $1,026.37   $1,026.35   $1,026.40