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	$138.97	7.847%	$149.875	$149.88	$149.90	$149.90
Purchase #2	$45.45	7.551%	$48.8819	$48.88	$48.90	$48.90
Purchase #3	$90.48	10.862%	$100.3079	$100.31	$100.30	$100.30
Purchase #4	$124.98	9.252%	$136.5431	$136.54	$136.55	$136.50
Purchase #5	$208.35	11.797%	$232.929	$232.93	$232.95	$232.90
Purchase #6	$82.37	4.828%	$86.3468	$86.35	$86.35	$86.30
Purchase #7	$97.68	13.851%	$111.2097	$111.21	$111.20	$111.20
7 purchase totals =	$788.28		$866.0934	$866.10	$866.15	$866.00