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	$145.82	9.629%	$159.861	$159.86	$159.85	$159.90
Purchase #2	$225.72	12.567%	$254.0862	$254.09	$254.10	$254.10
Purchase #3	$79.60	12.862%	$89.8382	$89.84	$89.85	$89.80
Purchase #4	$212.91	8.801%	$231.6482	$231.65	$231.65	$231.60
Purchase #5	$184.38	3.430%	$190.7042	$190.70	$190.70	$190.70
Purchase #6	$169.36	7.362%	$181.8283	$181.83	$181.85	$181.80
Purchase #7	$7.67	13.643%	$8.7164	$8.72	$8.70	$8.70
7 purchase totals =	$1,025.46		$1,116.6825	$1,116.69	$1,116.70	$1,116.60