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 $70.32   10.426%   $77.6516   $77.65   $77.65   $77.70  
  Purchase #2 $88.55   7.270%   $94.9876   $94.99   $95.00   $95.00  
  Purchase #3 $190.81   5.673%   $201.6347   $201.63   $201.65   $201.60  
  Purchase #4 $166.30   10.184%   $183.236   $183.24   $183.25   $183.20  
  Purchase #5 $149.42   12.650%   $168.3216   $168.32   $168.30   $168.30  
  Purchase #6 $201.35   5.587%   $212.5994   $212.60   $212.60   $212.60  
  Purchase #7 $6.68   13.805%   $7.6022   $7.60   $7.60   $7.60  
  7 purchase totals = $873.43       $946.0331   $946.03   $946.05   $946.00