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	$91.32	11.273%	$101.6145	$101.61	$101.60	$101.60
Purchase #2	$52.77	12.635%	$59.4375	$59.44	$59.45	$59.40
Purchase #3	$116.51	13.220%	$131.9126	$131.91	$131.90	$131.90
Purchase #4	$37.60	6.825%	$40.1662	$40.17	$40.15	$40.20
Purchase #5	$141.90	8.549%	$154.031	$154.03	$154.05	$154.00
Purchase #6	$11.54	6.138%	$12.2483	$12.25	$12.25	$12.20
Purchase #7	$33.28	11.519%	$37.1135	$37.11	$37.10	$37.10
7 purchase totals =	$484.92		$536.5236	$536.52	$536.50	$536.40