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 $62.74   7.615%   $67.5177   $67.52   $67.50   $67.50  
  Purchase #2 $241.93   5.148%   $254.3846   $254.38   $254.40   $254.40  
  Purchase #3 $110.90   10.127%   $122.1308   $122.13   $122.15   $122.10  
  Purchase #4 $187.93   3.237%   $194.0133   $194.01   $194.00   $194.00  
  Purchase #5 $56.53   7.206%   $60.6036   $60.60   $60.60   $60.60  
  Purchase #6 $220.49   7.444%   $236.9033   $236.90   $236.90   $236.90  
  Purchase #7 $111.73   3.226%   $115.3344   $115.33   $115.35   $115.30  
  7 purchase totals = $992.25       $1,050.8877   $1,050.87   $1,050.90   $1,050.80