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 $43.53   10.397%   $48.0558   $48.06   $48.05   $48.10  
  Purchase #2 $215.64   9.397%   $235.9037   $235.90   $235.90   $235.90  
  Purchase #3 $228.91   4.343%   $238.8516   $238.85   $238.85   $238.90  
  Purchase #4 $95.77   13.138%   $108.3523   $108.35   $108.35   $108.40  
  Purchase #5 $64.28   10.443%   $70.9928   $70.99   $71.00   $71.00  
  Purchase #6 $189.99   11.811%   $212.4297   $212.43   $212.45   $212.40  
  Purchase #7 $103.72   7.784%   $111.7936   $111.79   $111.80   $111.80  
  7 purchase totals = $941.84       $1,026.3795   $1,026.37   $1,026.40   $1,026.50