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	$188.66	4.251%	$196.6799	$196.68	$196.70	$196.70
Purchase #2	$25.96	13.695%	$29.5152	$29.52	$29.50	$29.50
Purchase #3	$74.89	4.610%	$78.3424	$78.34	$78.35	$78.30
Purchase #4	$81.47	5.434%	$85.8971	$85.90	$85.90	$85.90
Purchase #5	$68.25	10.740%	$75.5801	$75.58	$75.60	$75.60
Purchase #6	$219.91	10.468%	$242.9302	$242.93	$242.95	$242.90
Purchase #7	$85.38	6.863%	$91.2396	$91.24	$91.25	$91.20
7 purchase totals =	$744.52		$800.1845	$800.19	$800.25	$800.10