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	$175.41	8.159%	$189.7217	$189.72	$189.70	$189.70
Purchase #2	$146.73	6.601%	$156.4156	$156.42	$156.40	$156.40
Purchase #3	$156.87	5.483%	$165.4712	$165.47	$165.45	$165.50
Purchase #4	$184.85	12.666%	$208.2631	$208.26	$208.25	$208.30
Purchase #5	$19.42	10.561%	$21.4709	$21.47	$21.45	$21.50
Purchase #6	$151.55	10.188%	$166.9899	$166.99	$167.00	$167.00
Purchase #7	$110.89	13.691%	$126.0719	$126.07	$126.05	$126.10
7 purchase totals =	$945.72		$1,034.4043	$1,034.40	$1,034.30	$1,034.50