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 $211.53   9.693%   $232.0336   $232.03   $232.05   $232.00  
  Purchase #2 $230.96   9.399%   $252.6679   $252.67   $252.65   $252.70  
  Purchase #3 $36.85   12.793%   $41.5642   $41.56   $41.55   $41.60  
  Purchase #4 $62.41   13.531%   $70.8547   $70.85   $70.85   $70.90  
  Purchase #5 $195.65   4.718%   $204.8808   $204.88   $204.90   $204.90  
  Purchase #6 $238.99   12.646%   $269.2127   $269.21   $269.20   $269.20  
  Purchase #7 $156.93   8.391%   $170.098   $170.10   $170.10   $170.10  
  7 purchase totals = $1,133.32       $1,241.3119   $1,241.30   $1,241.30   $1,241.40