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	$176.68	7.566%	$190.0476	$190.05	$190.05	$190.00
Purchase #2	$240.28	10.826%	$266.2927	$266.29	$266.30	$266.30
Purchase #3	$156.85	10.862%	$173.887	$173.89	$173.90	$173.90
Purchase #4	$246.45	8.398%	$267.1469	$267.15	$267.15	$267.10
Purchase #5	$100.94	5.404%	$106.3948	$106.39	$106.40	$106.40
Purchase #6	$133.43	12.652%	$150.3116	$150.31	$150.30	$150.30
Purchase #7	$79.94	12.109%	$89.6199	$89.62	$89.60	$89.60
7 purchase totals =	$1,134.57		$1,243.7005	$1,243.70	$1,243.70	$1,243.60