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	$133.67	13.180%	$151.2877	$151.29	$151.30	$151.30
Purchase #2	$29.72	10.478%	$32.8341	$32.83	$32.85	$32.80
Purchase #3	$81.35	13.662%	$92.464	$92.46	$92.45	$92.50
Purchase #4	$201.68	5.588%	$212.9499	$212.95	$212.95	$212.90
Purchase #5	$29.54	11.858%	$33.0429	$33.04	$33.05	$33.00
Purchase #6	$23.40	7.149%	$25.0729	$25.07	$25.05	$25.10
Purchase #7	$73.33	7.539%	$78.8583	$78.86	$78.85	$78.90
7 purchase totals =	$572.69		$626.5098	$626.50	$626.50	$626.50