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	$33.87	11.749%	$37.8494	$37.85	$37.85	$37.80
Purchase #2	$233.85	3.479%	$241.9856	$241.99	$242.00	$242.00
Purchase #3	$43.42	7.165%	$46.531	$46.53	$46.55	$46.50
Purchase #4	$81.73	6.155%	$86.7605	$86.76	$86.75	$86.80
Purchase #5	$91.67	11.651%	$102.3505	$102.35	$102.35	$102.40
Purchase #6	$51.52	11.168%	$57.2738	$57.27	$57.25	$57.30
Purchase #7	$134.84	12.680%	$151.9377	$151.94	$151.95	$151.90
7 purchase totals =	$670.90		$724.6885	$724.69	$724.70	$724.70