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	$162.45	10.618%	$179.6989	$179.70	$179.70	$179.70
Purchase #2	$96.29	5.114%	$101.2143	$101.21	$101.20	$101.20
Purchase #3	$237.66	4.770%	$248.9964	$249.00	$249.00	$249.00
Purchase #4	$231.67	3.766%	$240.3947	$240.39	$240.40	$240.40
Purchase #5	$40.33	13.373%	$45.7233	$45.72	$45.70	$45.70
Purchase #6	$86.41	10.696%	$95.6524	$95.65	$95.65	$95.70
Purchase #7	$151.51	12.310%	$170.1609	$170.16	$170.15	$170.20
7 purchase totals =	$1,006.32		$1,081.8409	$1,081.83	$1,081.80	$1,081.90