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	$146.91	12.453%	$165.2047	$165.20	$165.20	$165.20
Purchase #2	$76.46	5.701%	$80.819	$80.82	$80.80	$80.80
Purchase #3	$173.51	8.417%	$188.1143	$188.11	$188.10	$188.10
Purchase #4	$184.51	6.640%	$196.7615	$196.76	$196.75	$196.80
Purchase #5	$127.68	5.653%	$134.8978	$134.90	$134.90	$134.90
Purchase #6	$158.76	9.726%	$174.201	$174.20	$174.20	$174.20
Purchase #7	$155.52	11.562%	$173.5012	$173.50	$173.50	$173.50
7 purchase totals =	$1,023.35		$1,113.4995	$1,113.49	$1,113.45	$1,113.50