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 $185.73   11.871%   $207.778   $207.78   $207.80   $207.80  
  Purchase #2 $34.83   5.146%   $36.6224   $36.62   $36.60   $36.60  
  Purchase #3 $213.75   13.121%   $241.7961   $241.80   $241.80   $241.80  
  Purchase #4 $145.75   5.576%   $153.877   $153.88   $153.90   $153.90  
  Purchase #5 $179.51   3.405%   $185.6223   $185.62   $185.60   $185.60  
  Purchase #6 $159.68   11.311%   $177.7414   $177.74   $177.75   $177.70  
  Purchase #7 $140.52   7.103%   $150.5011   $150.50   $150.50   $150.50  
  7 purchase totals = $1,059.77       $1,153.9383   $1,153.94   $1,153.95   $1,153.90