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 $62.59   8.446%   $67.8764   $67.88   $67.90   $67.90  
  Purchase #2 $132.95   6.108%   $141.0706   $141.07   $141.05   $141.10  
  Purchase #3 $197.48   11.136%   $219.4714   $219.47   $219.45   $219.50  
  Purchase #4 $225.84   12.562%   $254.21   $254.21   $254.20   $254.20  
  Purchase #5 $196.70   4.376%   $205.3076   $205.31   $205.30   $205.30  
  Purchase #6 $203.72   8.421%   $220.8753   $220.88   $220.90   $220.90  
  Purchase #7 $77.63   7.202%   $83.2209   $83.22   $83.20   $83.20  
  7 purchase totals = $1,096.91       $1,192.0322   $1,192.04   $1,192.00   $1,192.10