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	$79.75	9.447%	$87.284	$87.28	$87.30	$87.30
Purchase #2	$88.90	7.727%	$95.7693	$95.77	$95.75	$95.80
Purchase #3	$101.27	10.322%	$111.7231	$111.72	$111.70	$111.70
Purchase #4	$195.51	7.294%	$209.7705	$209.77	$209.75	$209.80
Purchase #5	$200.88	5.324%	$211.5749	$211.57	$211.55	$211.60
Purchase #6	$124.67	11.714%	$139.2738	$139.27	$139.25	$139.30
Purchase #7	$42.66	5.168%	$44.8647	$44.86	$44.85	$44.90
7 purchase totals =	$833.64		$900.2603	$900.24	$900.15	$900.40