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	$198.38	12.247%	$222.6756	$222.68	$222.70	$222.70
Purchase #2	$52.73	4.820%	$55.2716	$55.27	$55.25	$55.30
Purchase #3	$56.72	3.816%	$58.8844	$58.88	$58.90	$58.90
Purchase #4	$79.57	13.679%	$90.4544	$90.45	$90.45	$90.50
Purchase #5	$89.69	6.425%	$95.4526	$95.45	$95.45	$95.50
Purchase #6	$114.70	8.662%	$124.6353	$124.64	$124.65	$124.60
Purchase #7	$229.71	8.143%	$248.4153	$248.42	$248.40	$248.40
7 purchase totals =	$821.50		$895.7892	$895.79	$895.80	$895.90