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	$183.78	3.854%	$190.8629	$190.86	$190.85	$190.90
Purchase #2	$186.78	10.266%	$205.9548	$205.95	$205.95	$206.00
Purchase #3	$64.87	8.507%	$70.3885	$70.39	$70.40	$70.40
Purchase #4	$92.30	8.532%	$100.175	$100.18	$100.20	$100.20
Purchase #5	$79.89	7.521%	$85.8985	$85.90	$85.90	$85.90
Purchase #6	$152.51	13.673%	$173.3627	$173.36	$173.35	$173.40
Purchase #7	$10.81	10.207%	$11.9134	$11.91	$11.90	$11.90
7 purchase totals =	$770.94		$838.5558	$838.55	$838.55	$838.70