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 $226.96   7.614%   $244.2407   $244.24   $244.25   $244.20  
  Purchase #2 $32.98   9.133%   $35.9921   $35.99   $36.00   $36.00  
  Purchase #3 $71.30   12.360%   $80.1127   $80.11   $80.10   $80.10  
  Purchase #4 $140.94   8.275%   $152.6028   $152.60   $152.60   $152.60  
  Purchase #5 $189.60   8.204%   $205.1548   $205.15   $205.15   $205.20  
  Purchase #6 $196.77   7.658%   $211.8386   $211.84   $211.85   $211.80  
  Purchase #7 $134.39   6.188%   $142.7061   $142.71   $142.70   $142.70  
  7 purchase totals = $992.94       $1,072.6478   $1,072.64   $1,072.65   $1,072.60