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 $60.80   11.551%   $67.823   $67.82   $67.80   $67.80  
  Purchase #2 $232.98   5.164%   $245.0111   $245.01   $245.00   $245.00  
  Purchase #3 $51.40   12.152%   $57.6461   $57.65   $57.65   $57.60  
  Purchase #4 $181.95   13.531%   $206.5697   $206.57   $206.55   $206.60  
  Purchase #5 $115.80   10.772%   $128.274   $128.27   $128.25   $128.30  
  Purchase #6 $201.44   4.191%   $209.8824   $209.88   $209.90   $209.90  
  Purchase #7 $246.77   12.152%   $276.7575   $276.76   $276.75   $276.80  
  7 purchase totals = $1,091.14       $1,191.9638   $1,191.96   $1,191.90   $1,192.00