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 $223.87   10.669%   $247.7547   $247.75   $247.75   $247.80  
  Purchase #2 $96.38   10.185%   $106.1963   $106.20   $106.20   $106.20  
  Purchase #3 $55.59   10.774%   $61.5793   $61.58   $61.60   $61.60  
  Purchase #4 $133.44   11.151%   $148.3199   $148.32   $148.30   $148.30  
  Purchase #5 $192.51   5.277%   $202.6688   $202.67   $202.65   $202.70  
  Purchase #6 $133.79   11.617%   $149.3324   $149.33   $149.35   $149.30  
  Purchase #7 $120.47   5.809%   $127.4681   $127.47   $127.45   $127.50  
  7 purchase totals = $956.05       $1,043.3195   $1,043.32   $1,043.30   $1,043.40