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 $174.96   11.538%   $195.1469   $195.15   $195.15   $195.10  
  Purchase #2 $181.93   4.791%   $190.6463   $190.65   $190.65   $190.60  
  Purchase #3 $17.90   9.726%   $19.641   $19.64   $19.65   $19.60  
  Purchase #4 $107.44   10.263%   $118.4666   $118.47   $118.45   $118.50  
  Purchase #5 $168.52   8.384%   $182.6487   $182.65   $182.65   $182.60  
  Purchase #6 $200.31   8.869%   $218.0755   $218.08   $218.10   $218.10  
  Purchase #7 $181.54   10.373%   $200.3711   $200.37   $200.35   $200.40  
  7 purchase totals = $1,032.60       $1,124.9961   $1,125.01   $1,125.00   $1,124.90