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 $104.38   8.672%   $113.4318   $113.43   $113.45   $113.40  
  Purchase #2 $205.69   10.838%   $227.9827   $227.98   $228.00   $228.00  
  Purchase #3 $184.74   5.349%   $194.6217   $194.62   $194.60   $194.60  
  Purchase #4 $80.33   9.424%   $87.9003   $87.90   $87.90   $87.90  
  Purchase #5 $54.91   5.650%   $58.0124   $58.01   $58.00   $58.00  
  Purchase #6 $175.88   11.836%   $196.6972   $196.70   $196.70   $196.70  
  Purchase #7 $202.43   8.332%   $219.2965   $219.30   $219.30   $219.30  
  7 purchase totals = $1,008.36       $1,097.9426   $1,097.94   $1,097.95   $1,097.90