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	$22.83	5.594%	$24.1071	$24.11	$24.10	$24.10
Purchase #2	$112.71	13.451%	$127.8706	$127.87	$127.85	$127.90
Purchase #3	$233.67	7.303%	$250.7349	$250.73	$250.75	$250.70
Purchase #4	$54.79	13.592%	$62.2371	$62.24	$62.25	$62.20
Purchase #5	$225.60	6.411%	$240.0632	$240.06	$240.05	$240.10
Purchase #6	$169.53	7.396%	$182.0684	$182.07	$182.05	$182.10
Purchase #7	$230.66	10.336%	$254.501	$254.50	$254.50	$254.50
7 purchase totals =	$1,049.79		$1,141.5823	$1,141.58	$1,141.55	$1,141.60