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 $57.95   8.415%   $62.8265   $62.83   $62.85   $62.80  
  Purchase #2 $192.27   4.647%   $201.2048   $201.20   $201.20   $201.20  
  Purchase #3 $84.38   11.345%   $93.9529   $93.95   $93.95   $94.00  
  Purchase #4 $117.96   7.457%   $126.7563   $126.76   $126.75   $126.80  
  Purchase #5 $200.69   11.372%   $223.5125   $223.51   $223.50   $223.50  
  Purchase #6 $243.65   7.683%   $262.3696   $262.37   $262.35   $262.40  
  Purchase #7 $31.70   8.852%   $34.5061   $34.51   $34.50   $34.50  
  7 purchase totals = $928.60       $1,005.1287   $1,005.13   $1,005.10   $1,005.20