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	$98.53	13.679%	$112.0079	$112.01	$112.00	$112.00
Purchase #2	$146.78	10.655%	$162.4194	$162.42	$162.40	$162.40
Purchase #3	$168.71	12.821%	$190.3403	$190.34	$190.35	$190.30
Purchase #4	$29.94	7.118%	$32.0711	$32.07	$32.05	$32.10
Purchase #5	$133.72	11.678%	$149.3358	$149.34	$149.35	$149.30
Purchase #6	$247.95	4.505%	$259.1201	$259.12	$259.10	$259.10
Purchase #7	$195.82	11.191%	$217.7342	$217.73	$217.75	$217.70
7 purchase totals =	$1,021.45		$1,123.0288	$1,123.03	$1,123.00	$1,122.90