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	$63.39	12.417%	$71.2611	$71.26	$71.25	$71.30
Purchase #2	$208.83	12.140%	$234.182	$234.18	$234.20	$234.20
Purchase #3	$164.50	11.127%	$182.8039	$182.80	$182.80	$182.80
Purchase #4	$109.51	12.740%	$123.4616	$123.46	$123.45	$123.50
Purchase #5	$164.52	9.806%	$180.6528	$180.65	$180.65	$180.70
Purchase #6	$200.67	11.385%	$223.5163	$223.52	$223.50	$223.50
Purchase #7	$213.38	5.646%	$225.4274	$225.43	$225.45	$225.40
7 purchase totals =	$1,124.80		$1,241.3051	$1,241.30	$1,241.30	$1,241.40