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 $217.51   12.644%   $245.012   $245.01   $245.00   $245.00  
  Purchase #2 $10.52   4.392%   $10.982   $10.98   $11.00   $11.00  
  Purchase #3 $104.60   12.292%   $117.4574   $117.46   $117.45   $117.50  
  Purchase #4 $225.81   12.841%   $254.8063   $254.81   $254.80   $254.80  
  Purchase #5 $126.80   6.591%   $135.1574   $135.16   $135.15   $135.20  
  Purchase #6 $206.44   13.863%   $235.0588   $235.06   $235.05   $235.10  
  Purchase #7 $187.79   8.263%   $203.3071   $203.31   $203.30   $203.30  
  7 purchase totals = $1,079.47       $1,201.7810   $1,201.79   $1,201.75   $1,201.90