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	$107.85	3.776%	$111.9224	$111.92	$111.90	$111.90
Purchase #2	$20.96	6.860%	$22.3979	$22.40	$22.40	$22.40
Purchase #3	$55.67	11.513%	$62.0793	$62.08	$62.10	$62.10
Purchase #4	$50.31	7.571%	$54.119	$54.12	$54.10	$54.10
Purchase #5	$237.57	5.195%	$249.9118	$249.91	$249.90	$249.90
Purchase #6	$140.45	11.838%	$157.0765	$157.08	$157.10	$157.10
Purchase #7	$50.51	5.614%	$53.3456	$53.35	$53.35	$53.30
7 purchase totals =	$663.32		$710.8525	$710.86	$710.85	$710.80