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 $60.33   5.427%   $63.6041   $63.60   $63.60   $63.60  
  Purchase #2 $201.95   9.224%   $220.5779   $220.58   $220.60   $220.60  
  Purchase #3 $20.55   10.453%   $22.6981   $22.70   $22.70   $22.70  
  Purchase #4 $201.83   7.702%   $217.3749   $217.37   $217.35   $217.40  
  Purchase #5 $231.47   6.869%   $247.3697   $247.37   $247.35   $247.40  
  Purchase #6 $244.84   10.597%   $270.7857   $270.79   $270.80   $270.80  
  Purchase #7 $37.79   10.812%   $41.8759   $41.88   $41.90   $41.90  
  7 purchase totals = $998.76       $1,084.2863   $1,084.29   $1,084.30   $1,084.40