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 $92.61   3.694%   $96.031   $96.03   $96.05   $96.00  
  Purchase #2 $110.87   5.327%   $116.776   $116.78   $116.80   $116.80  
  Purchase #3 $165.81   12.631%   $186.7535   $186.75   $186.75   $186.80  
  Purchase #4 $156.49   6.387%   $166.485   $166.49   $166.50   $166.50  
  Purchase #5 $201.56   5.201%   $212.0431   $212.04   $212.05   $212.00  
  Purchase #6 $48.45   7.492%   $52.0799   $52.08   $52.10   $52.10  
  Purchase #7 $236.94   7.467%   $254.6323   $254.63   $254.65   $254.60  
  7 purchase totals = $1,012.73       $1,084.8008   $1,084.80   $1,084.90   $1,084.80