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	$99.72	11.751%	$111.4381	$111.44	$111.45	$111.40
Purchase #2	$225.77	9.362%	$246.9066	$246.91	$246.90	$246.90
Purchase #3	$78.77	12.258%	$88.4256	$88.43	$88.45	$88.40
Purchase #4	$173.98	12.212%	$195.2264	$195.23	$195.25	$195.20
Purchase #5	$49.83	5.288%	$52.465	$52.47	$52.45	$52.50
Purchase #6	$180.43	11.445%	$201.0802	$201.08	$201.10	$201.10
Purchase #7	$229.60	11.530%	$256.0729	$256.07	$256.05	$256.10
7 purchase totals =	$1,038.10		$1,151.6148	$1,151.63	$1,151.65	$1,151.60