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	$118.34	10.395%	$130.6414	$130.64	$130.65	$130.60
Purchase #2	$72.89	12.795%	$82.2163	$82.22	$82.20	$82.20
Purchase #3	$196.88	13.506%	$223.4706	$223.47	$223.45	$223.50
Purchase #4	$61.83	7.762%	$66.6292	$66.63	$66.65	$66.60
Purchase #5	$56.51	11.704%	$63.1239	$63.12	$63.10	$63.10
Purchase #6	$133.28	6.322%	$141.706	$141.71	$141.70	$141.70
Purchase #7	$136.44	13.235%	$154.4978	$154.50	$154.50	$154.50
7 purchase totals =	$776.17		$862.2852	$862.29	$862.25	$862.20