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	$155.31	13.181%	$175.7814	$175.78	$175.80	$175.80
Purchase #2	$154.94	13.680%	$176.1358	$176.14	$176.15	$176.10
Purchase #3	$156.58	5.712%	$165.5238	$165.52	$165.50	$165.50
Purchase #4	$89.87	5.315%	$94.6466	$94.65	$94.65	$94.60
Purchase #5	$138.38	12.285%	$155.38	$155.38	$155.40	$155.40
Purchase #6	$228.43	11.331%	$254.3134	$254.31	$254.30	$254.30
Purchase #7	$227.80	12.502%	$256.2796	$256.28	$256.30	$256.30
7 purchase totals =	$1,151.31		$1,278.0606	$1,278.06	$1,278.10	$1,278.00