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 $59.75   8.704%   $64.9506   $64.95   $64.95   $65.00  
  Purchase #2 $120.70   12.345%   $135.6004   $135.60   $135.60   $135.60  
  Purchase #3 $238.35   3.220%   $246.0249   $246.02   $246.00   $246.00  
  Purchase #4 $210.75   3.689%   $218.5246   $218.52   $218.50   $218.50  
  Purchase #5 $214.40   12.378%   $240.9384   $240.94   $240.95   $240.90  
  Purchase #6 $85.34   11.336%   $95.0141   $95.01   $95.00   $95.00  
  Purchase #7 $178.30   7.798%   $192.2038   $192.20   $192.20   $192.20  
  7 purchase totals = $1,107.59       $1,193.2568   $1,193.24   $1,193.20   $1,193.20