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 $228.78   5.540%   $241.4544   $241.45   $241.45   $241.50  
  Purchase #2 $219.83   8.841%   $239.2652   $239.27   $239.25   $239.30  
  Purchase #3 $161.65   8.281%   $175.0362   $175.04   $175.05   $175.00  
  Purchase #4 $228.40   4.236%   $238.075   $238.08   $238.10   $238.10  
  Purchase #5 $167.90   9.576%   $183.9781   $183.98   $184.00   $184.00  
  Purchase #6 $213.99   7.530%   $230.1034   $230.10   $230.10   $230.10  
  Purchase #7 $87.64   7.341%   $94.0737   $94.07   $94.05   $94.10  
  7 purchase totals = $1,308.19       $1,401.9860   $1,401.99   $1,402.00   $1,402.10