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 $54.46   13.777%   $61.963   $61.96   $61.95   $62.00  
  Purchase #2 $126.42   8.369%   $137.0001   $137.00   $137.00   $137.00  
  Purchase #3 $83.84   8.119%   $90.647   $90.65   $90.65   $90.60  
  Purchase #4 $209.66   11.264%   $233.2761   $233.28   $233.30   $233.30  
  Purchase #5 $75.46   13.235%   $85.4471   $85.45   $85.45   $85.40  
  Purchase #6 $192.58   7.346%   $206.7269   $206.73   $206.75   $206.70  
  Purchase #7 $202.49   12.715%   $228.2366   $228.24   $228.25   $228.20  
  7 purchase totals = $944.91       $1,043.2968   $1,043.31   $1,043.35   $1,043.20