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	$66.58	7.299%	$71.4397	$71.44	$71.45	$71.40
Purchase #2	$140.45	5.654%	$148.391	$148.39	$148.40	$148.40
Purchase #3	$193.89	13.403%	$219.8771	$219.88	$219.90	$219.90
Purchase #4	$31.95	5.394%	$33.6734	$33.67	$33.65	$33.70
Purchase #5	$57.58	5.236%	$60.5949	$60.59	$60.60	$60.60
Purchase #6	$230.41	6.194%	$244.6816	$244.68	$244.70	$244.70
Purchase #7	$98.94	12.636%	$111.4421	$111.44	$111.45	$111.40
7 purchase totals =	$819.80		$890.0998	$890.09	$890.15	$890.10