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	$202.64	7.790%	$218.4257	$218.43	$218.45	$218.40
Purchase #2	$131.72	10.757%	$145.8891	$145.89	$145.90	$145.90
Purchase #3	$248.32	12.662%	$279.7623	$279.76	$279.75	$279.80
Purchase #4	$191.38	4.205%	$199.4275	$199.43	$199.45	$199.40
Purchase #5	$218.79	3.555%	$226.568	$226.57	$226.55	$226.60
Purchase #6	$71.77	4.725%	$75.1611	$75.16	$75.15	$75.20
Purchase #7	$26.25	3.679%	$27.2157	$27.22	$27.20	$27.20
7 purchase totals =	$1,090.87		$1,172.4494	$1,172.46	$1,172.45	$1,172.50