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	$56.59	5.433%	$59.6645	$59.66	$59.65	$59.70
Purchase #2	$213.28	3.774%	$221.3292	$221.33	$221.35	$221.30
Purchase #3	$245.34	3.716%	$254.4568	$254.46	$254.45	$254.50
Purchase #4	$71.85	3.648%	$74.4711	$74.47	$74.45	$74.50
Purchase #5	$127.81	12.571%	$143.877	$143.88	$143.90	$143.90
Purchase #6	$110.40	6.145%	$117.1841	$117.18	$117.20	$117.20
Purchase #7	$122.74	11.294%	$136.6023	$136.60	$136.60	$136.60
7 purchase totals =	$948.01		$1,007.5850	$1,007.58	$1,007.60	$1,007.70