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 $62.82   9.765%   $68.9544   $68.95   $68.95   $69.00  
  Purchase #2 $168.68   10.279%   $186.0186   $186.02   $186.00   $186.00  
  Purchase #3 $161.85   13.837%   $184.2452   $184.25   $184.25   $184.20  
  Purchase #4 $42.40   4.332%   $44.2368   $44.24   $44.25   $44.20  
  Purchase #5 $213.64   7.771%   $230.242   $230.24   $230.25   $230.20  
  Purchase #6 $128.64   10.353%   $141.9581   $141.96   $141.95   $142.00  
  Purchase #7 $214.57   6.648%   $228.8346   $228.83   $228.85   $228.80  
  7 purchase totals = $992.60       $1,084.4897   $1,084.49   $1,084.50   $1,084.40