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 $63.36   9.726%   $69.5224   $69.52   $69.50   $69.50  
  Purchase #2 $226.35   6.665%   $241.4362   $241.44   $241.45   $241.40  
  Purchase #3 $231.59   8.517%   $251.3145   $251.31   $251.30   $251.30  
  Purchase #4 $147.31   12.562%   $165.8151   $165.82   $165.80   $165.80  
  Purchase #5 $144.82   6.544%   $154.297   $154.30   $154.30   $154.30  
  Purchase #6 $87.93   13.332%   $99.6528   $99.65   $99.65   $99.70  
  Purchase #7 $189.41   7.372%   $203.3733   $203.37   $203.35   $203.40  
  7 purchase totals = $1,090.77       $1,185.4113   $1,185.41   $1,185.35   $1,185.40