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	$177.35	6.525%	$188.9221	$188.92	$188.90	$188.90
Purchase #2	$234.56	8.501%	$254.4999	$254.50	$254.50	$254.50
Purchase #3	$196.35	6.458%	$209.0303	$209.03	$209.05	$209.00
Purchase #4	$158.69	12.861%	$179.0991	$179.10	$179.10	$179.10
Purchase #5	$206.46	13.864%	$235.0836	$235.08	$235.10	$235.10
Purchase #6	$170.26	5.615%	$179.8201	$179.82	$179.80	$179.80
Purchase #7	$111.92	3.741%	$116.1069	$116.11	$116.10	$116.10
7 purchase totals =	$1,255.59		$1,362.5620	$1,362.56	$1,362.55	$1,362.50