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	$118.63	7.416%	$127.4276	$127.43	$127.45	$127.40
Purchase #2	$166.31	13.540%	$188.8284	$188.83	$188.85	$188.80
Purchase #3	$225.61	7.414%	$242.3367	$242.34	$242.35	$242.30
Purchase #4	$50.47	10.265%	$55.6507	$55.65	$55.65	$55.70
Purchase #5	$107.40	5.461%	$113.2651	$113.27	$113.25	$113.30
Purchase #6	$83.70	10.700%	$92.6559	$92.66	$92.65	$92.70
Purchase #7	$214.78	6.716%	$229.2046	$229.20	$229.20	$229.20
7 purchase totals =	$966.90		$1,049.3690	$1,049.38	$1,049.40	$1,049.40