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	$131.50	12.321%	$147.7021	$147.70	$147.70	$147.70
Purchase #2	$62.45	13.165%	$70.6715	$70.67	$70.65	$70.70
Purchase #3	$58.92	4.744%	$61.7152	$61.72	$61.70	$61.70
Purchase #4	$242.39	6.485%	$258.109	$258.11	$258.10	$258.10
Purchase #5	$100.30	11.375%	$111.7091	$111.71	$111.70	$111.70
Purchase #6	$209.90	4.418%	$219.1734	$219.17	$219.15	$219.20
Purchase #7	$36.44	8.649%	$39.5917	$39.59	$39.60	$39.60
7 purchase totals =	$841.90		$908.6720	$908.67	$908.60	$908.70