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	$152.81	9.557%	$167.4141	$167.41	$167.40	$167.40
Purchase #2	$142.46	7.310%	$152.8738	$152.87	$152.85	$152.90
Purchase #3	$206.59	5.312%	$217.5641	$217.56	$217.55	$217.60
Purchase #4	$120.84	5.431%	$127.4028	$127.40	$127.40	$127.40
Purchase #5	$66.61	12.199%	$74.7358	$74.74	$74.75	$74.70
Purchase #6	$206.76	10.535%	$228.5422	$228.54	$228.55	$228.50
Purchase #7	$173.70	10.451%	$191.8534	$191.85	$191.85	$191.90
7 purchase totals =	$1,069.77		$1,160.3862	$1,160.37	$1,160.35	$1,160.40