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	$159.43	13.639%	$181.1747	$181.17	$181.15	$181.20
Purchase #2	$171.34	10.518%	$189.3615	$189.36	$189.35	$189.40
Purchase #3	$74.68	6.350%	$79.4222	$79.42	$79.40	$79.40
Purchase #4	$229.28	6.130%	$243.3349	$243.33	$243.35	$243.30
Purchase #5	$136.67	3.812%	$141.8799	$141.88	$141.90	$141.90
Purchase #6	$73.68	13.563%	$83.6732	$83.67	$83.65	$83.70
Purchase #7	$123.63	3.146%	$127.5194	$127.52	$127.50	$127.50
7 purchase totals =	$968.71		$1,046.3658	$1,046.35	$1,046.30	$1,046.40