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	$184.69	7.603%	$198.732	$198.73	$198.75	$198.70
Purchase #2	$61.34	12.209%	$68.829	$68.83	$68.85	$68.80
Purchase #3	$149.66	6.191%	$158.9255	$158.93	$158.95	$158.90
Purchase #4	$46.29	12.426%	$52.042	$52.04	$52.05	$52.00
Purchase #5	$148.31	4.451%	$154.9113	$154.91	$154.90	$154.90
Purchase #6	$249.74	5.643%	$263.8328	$263.83	$263.85	$263.80
Purchase #7	$64.80	11.218%	$72.0693	$72.07	$72.05	$72.10
7 purchase totals =	$904.83		$969.3419	$969.34	$969.40	$969.20