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 $89.27   6.801%   $95.3413   $95.34   $95.35   $95.30  
  Purchase #2 $91.85   3.378%   $94.9527   $94.95   $94.95   $95.00  
  Purchase #3 $241.73   12.546%   $272.0574   $272.06   $272.05   $272.10  
  Purchase #4 $159.99   11.779%   $178.8352   $178.84   $178.85   $178.80  
  Purchase #5 $168.38   11.413%   $187.5972   $187.60   $187.60   $187.60  
  Purchase #6 $60.36   5.305%   $63.5621   $63.56   $63.55   $63.60  
  Purchase #7 $233.57   4.258%   $243.5154   $243.52   $243.50   $243.50  
  7 purchase totals = $1,045.15       $1,135.8613   $1,135.87   $1,135.85   $1,135.90