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	$183.62	9.279%	$200.6581	$200.66	$200.65	$200.70
Purchase #2	$67.30	4.767%	$70.5082	$70.51	$70.50	$70.50
Purchase #3	$237.30	11.123%	$263.6949	$263.69	$263.70	$263.70
Purchase #4	$154.43	3.303%	$159.5308	$159.53	$159.55	$159.50
Purchase #5	$38.86	12.795%	$43.8321	$43.83	$43.85	$43.80
Purchase #6	$166.53	4.349%	$173.7724	$173.77	$173.75	$173.80
Purchase #7	$79.99	12.668%	$90.1231	$90.12	$90.10	$90.10
7 purchase totals =	$928.03		$1,002.1196	$1,002.11	$1,002.10	$1,002.10