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 $173.71   12.165%   $194.8418   $194.84   $194.85   $194.80  
  Purchase #2 $130.37   12.723%   $146.957   $146.96   $146.95   $147.00  
  Purchase #3 $43.49   12.169%   $48.7823   $48.78   $48.80   $48.80  
  Purchase #4 $228.67   11.151%   $254.169   $254.17   $254.15   $254.20  
  Purchase #5 $48.96   5.329%   $51.5691   $51.57   $51.55   $51.60  
  Purchase #6 $184.98   3.608%   $191.6541   $191.65   $191.65   $191.70  
  Purchase #7 $200.35   3.715%   $207.793   $207.79   $207.80   $207.80  
  7 purchase totals = $1,010.53       $1,095.7663   $1,095.76   $1,095.75   $1,095.90