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	$237.93	9.322%	$260.1098	$260.11	$260.10	$260.10
Purchase #2	$125.91	8.385%	$136.4676	$136.47	$136.45	$136.50
Purchase #3	$34.43	5.730%	$36.4028	$36.40	$36.40	$36.40
Purchase #4	$183.33	4.496%	$191.5725	$191.57	$191.55	$191.60
Purchase #5	$135.46	7.472%	$145.5816	$145.58	$145.60	$145.60
Purchase #6	$175.86	11.631%	$196.3143	$196.31	$196.30	$196.30
Purchase #7	$50.87	4.549%	$53.1841	$53.18	$53.20	$53.20
7 purchase totals =	$943.79		$1,019.6327	$1,019.62	$1,019.60	$1,019.70