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	$193.30	12.531%	$217.5224	$217.52	$217.50	$217.50
Purchase #2	$98.45	13.350%	$111.5931	$111.59	$111.60	$111.60
Purchase #3	$184.52	8.616%	$200.4182	$200.42	$200.40	$200.40
Purchase #4	$184.95	11.120%	$205.5164	$205.52	$205.50	$205.50
Purchase #5	$202.81	13.433%	$230.0535	$230.05	$230.05	$230.10
Purchase #6	$65.86	9.690%	$72.2418	$72.24	$72.25	$72.20
Purchase #7	$99.84	10.796%	$110.6187	$110.62	$110.60	$110.60
7 purchase totals =	$1,029.73		$1,147.9641	$1,147.96	$1,147.90	$1,147.90