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 $69.80   6.183%   $74.1157   $74.12   $74.10   $74.10  
  Purchase #2 $194.25   9.482%   $212.6688   $212.67   $212.65   $212.70  
  Purchase #3 $68.85   5.613%   $72.7146   $72.71   $72.70   $72.70  
  Purchase #4 $216.95   4.254%   $226.1791   $226.18   $226.20   $226.20  
  Purchase #5 $52.68   6.241%   $55.9678   $55.97   $55.95   $56.00  
  Purchase #6 $245.56   5.167%   $258.2481   $258.25   $258.25   $258.20  
  Purchase #7 $7.73   5.836%   $8.1811   $8.18   $8.20   $8.20  
  7 purchase totals = $855.82       $908.0752   $908.08   $908.05   $908.10