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 $184.49   5.641%   $194.8971   $194.90   $194.90   $194.90  
  Purchase #2 $114.35   3.155%   $117.9577   $117.96   $117.95   $118.00  
  Purchase #3 $85.30   3.823%   $88.561   $88.56   $88.55   $88.60  
  Purchase #4 $88.75   9.538%   $97.215   $97.22   $97.20   $97.20  
  Purchase #5 $15.41   6.667%   $16.4374   $16.44   $16.45   $16.40  
  Purchase #6 $54.26   12.119%   $60.8358   $60.84   $60.85   $60.80  
  Purchase #7 $189.74   3.354%   $196.1039   $196.10   $196.10   $196.10  
  7 purchase totals = $732.30       $772.0079   $772.02   $772.00   $772.00