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 $59.96   8.363%   $64.9745   $64.97   $64.95   $65.00  
  Purchase #2 $105.94   9.339%   $115.8337   $115.83   $115.85   $115.80  
  Purchase #3 $71.68   4.682%   $75.0361   $75.04   $75.05   $75.00  
  Purchase #4 $212.47   13.809%   $241.81   $241.81   $241.80   $241.80  
  Purchase #5 $205.83   5.155%   $216.4405   $216.44   $216.45   $216.40  
  Purchase #6 $211.41   8.819%   $230.0542   $230.05   $230.05   $230.10  
  Purchase #7 $199.27   4.258%   $207.7549   $207.75   $207.75   $207.80  
  7 purchase totals = $1,066.56       $1,151.9039   $1,151.89   $1,151.90   $1,151.90