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 $61.25   3.688%   $63.5089   $63.51   $63.50   $63.50  
  Purchase #2 $225.26   3.332%   $232.7657   $232.77   $232.75   $232.80  
  Purchase #3 $238.72   11.807%   $266.9057   $266.91   $266.90   $266.90  
  Purchase #4 $246.58   5.470%   $260.0679   $260.07   $260.05   $260.10  
  Purchase #5 $192.39   12.783%   $216.9832   $216.98   $217.00   $217.00  
  Purchase #6 $80.32   8.353%   $87.0291   $87.03   $87.05   $87.00  
  Purchase #7 $166.98   12.164%   $187.2914   $187.29   $187.30   $187.30  
  7 purchase totals = $1,211.50       $1,314.5519   $1,314.56   $1,314.55   $1,314.60