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	$191.34	7.440%	$205.5757	$205.58	$205.60	$205.60
Purchase #2	$248.95	8.363%	$269.7697	$269.77	$269.75	$269.80
Purchase #3	$162.25	13.711%	$184.4961	$184.50	$184.50	$184.50
Purchase #4	$249.50	6.281%	$265.1711	$265.17	$265.15	$265.20
Purchase #5	$21.33	5.454%	$22.4933	$22.49	$22.50	$22.50
Purchase #6	$230.31	10.852%	$255.3032	$255.30	$255.30	$255.30
Purchase #7	$85.27	7.680%	$91.8187	$91.82	$91.80	$91.80
7 purchase totals =	$1,188.95		$1,294.6278	$1,294.63	$1,294.60	$1,294.70