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	$157.88	7.375%	$169.5237	$169.52	$169.50	$169.50
Purchase #2	$64.50	8.322%	$69.8677	$69.87	$69.85	$69.90
Purchase #3	$179.31	3.316%	$185.2559	$185.26	$185.25	$185.30
Purchase #4	$190.78	7.128%	$204.3788	$204.38	$204.40	$204.40
Purchase #5	$139.71	3.621%	$144.7689	$144.77	$144.75	$144.80
Purchase #6	$198.82	13.374%	$225.4102	$225.41	$225.40	$225.40
Purchase #7	$17.69	10.617%	$19.5681	$19.57	$19.55	$19.60
7 purchase totals =	$948.69		$1,018.7733	$1,018.78	$1,018.70	$1,018.90