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	$250.89	13.388%	$284.4792	$284.48	$284.50	$284.50
Purchase #2	$173.52	11.556%	$193.572	$193.57	$193.55	$193.60
Purchase #3	$55.38	11.660%	$61.8373	$61.84	$61.85	$61.80
Purchase #4	$225.92	3.188%	$233.1223	$233.12	$233.10	$233.10
Purchase #5	$67.63	13.852%	$76.9981	$77.00	$77.00	$77.00
Purchase #6	$103.54	3.549%	$107.2146	$107.21	$107.20	$107.20
Purchase #7	$148.55	4.130%	$154.6851	$154.69	$154.70	$154.70
7 purchase totals =	$1,025.43		$1,111.9086	$1,111.91	$1,111.90	$1,111.90