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	$9.44	11.812%	$10.5551	$10.56	$10.55	$10.60
Purchase #2	$194.86	4.780%	$204.1743	$204.17	$204.15	$204.20
Purchase #3	$221.48	11.255%	$246.4076	$246.41	$246.40	$246.40
Purchase #4	$90.50	3.766%	$93.9082	$93.91	$93.90	$93.90
Purchase #5	$244.59	7.323%	$262.5013	$262.50	$262.50	$262.50
Purchase #6	$38.61	12.277%	$43.3501	$43.35	$43.35	$43.40
Purchase #7	$181.66	10.325%	$200.4164	$200.42	$200.40	$200.40
7 purchase totals =	$981.14		$1,061.3130	$1,061.32	$1,061.25	$1,061.40