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 $58.41   3.731%   $60.5893   $60.59   $60.60   $60.60  
  Purchase #2 $174.84   11.338%   $194.6634   $194.66   $194.65   $194.70  
  Purchase #3 $51.44   6.266%   $54.6632   $54.66   $54.65   $54.70  
  Purchase #4 $132.94   3.542%   $137.6487   $137.65   $137.65   $137.60  
  Purchase #5 $214.31   12.140%   $240.3272   $240.33   $240.35   $240.30  
  Purchase #6 $244.29   13.597%   $277.5061   $277.51   $277.50   $277.50  
  Purchase #7 $132.59   11.399%   $147.7039   $147.70   $147.70   $147.70  
  7 purchase totals = $1,008.82       $1,113.1018   $1,113.10   $1,113.10   $1,113.10