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 $39.35   11.704%   $43.9555   $43.96   $43.95   $44.00  
  Purchase #2 $46.53   9.842%   $51.1095   $51.11   $51.10   $51.10  
  Purchase #3 $165.88   9.139%   $181.0398   $181.04   $181.05   $181.00  
  Purchase #4 $225.90   10.544%   $249.7189   $249.72   $249.70   $249.70  
  Purchase #5 $169.64   9.119%   $185.1095   $185.11   $185.10   $185.10  
  Purchase #6 $247.52   11.280%   $275.4403   $275.44   $275.45   $275.40  
  Purchase #7 $130.25   12.477%   $146.5013   $146.50   $146.50   $146.50  
  7 purchase totals = $1,025.07       $1,132.8748   $1,132.88   $1,132.85   $1,132.80