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	$250.58	7.368%	$269.0427	$269.04	$269.05	$269.00
Purchase #2	$158.49	4.703%	$165.9438	$165.94	$165.95	$165.90
Purchase #3	$127.67	7.240%	$136.9133	$136.91	$136.90	$136.90
Purchase #4	$92.31	12.689%	$104.0232	$104.02	$104.00	$104.00
Purchase #5	$75.50	13.254%	$85.5068	$85.51	$85.50	$85.50
Purchase #6	$114.29	3.470%	$118.2559	$118.26	$118.25	$118.30
Purchase #7	$128.55	8.569%	$139.5654	$139.57	$139.55	$139.60
7 purchase totals =	$947.39		$1,019.2511	$1,019.25	$1,019.20	$1,019.20