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 $85.86   8.616%   $93.2577   $93.26   $93.25   $93.30  
  Purchase #2 $126.71   6.345%   $134.7497   $134.75   $134.75   $134.70  
  Purchase #3 $177.54   11.663%   $198.2465   $198.25   $198.25   $198.20  
  Purchase #4 $91.64   12.794%   $103.3644   $103.36   $103.35   $103.40  
  Purchase #5 $145.84   8.223%   $157.8324   $157.83   $157.85   $157.80  
  Purchase #6 $152.44   11.175%   $169.4752   $169.48   $169.50   $169.50  
  Purchase #7 $180.60   12.728%   $203.5868   $203.59   $203.60   $203.60  
  7 purchase totals = $960.63       $1,060.5127   $1,060.52   $1,060.55   $1,060.50