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	$126.60	12.580%	$142.5263	$142.53	$142.55	$142.50
Purchase #2	$31.39	4.538%	$32.8145	$32.81	$32.80	$32.80
Purchase #3	$31.72	3.401%	$32.7988	$32.80	$32.80	$32.80
Purchase #4	$229.40	10.413%	$253.2874	$253.29	$253.30	$253.30
Purchase #5	$92.43	4.621%	$96.7012	$96.70	$96.70	$96.70
Purchase #6	$173.46	13.124%	$196.2249	$196.22	$196.20	$196.20
Purchase #7	$222.83	13.625%	$253.1906	$253.19	$253.20	$253.20
7 purchase totals =	$907.83		$1,007.5437	$1,007.54	$1,007.55	$1,007.50