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 $56.60   3.595%   $58.6348   $58.63   $58.65   $58.60  
  Purchase #2 $245.26   5.646%   $259.1074   $259.11   $259.10   $259.10  
  Purchase #3 $83.94   4.832%   $87.996   $88.00   $88.00   $88.00  
  Purchase #4 $243.82   7.718%   $262.638   $262.64   $262.65   $262.60  
  Purchase #5 $203.83   3.678%   $211.3269   $211.33   $211.35   $211.30  
  Purchase #6 $207.64   3.799%   $215.5282   $215.53   $215.55   $215.50  
  Purchase #7 $19.27   4.712%   $20.178   $20.18   $20.20   $20.20  
  7 purchase totals = $1,060.36       $1,115.4093   $1,115.42   $1,115.50   $1,115.30