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	$233.30	9.738%	$256.0188	$256.02	$256.00	$256.00
Purchase #2	$114.31	11.335%	$127.267	$127.27	$127.25	$127.30
Purchase #3	$120.31	13.768%	$136.8743	$136.87	$136.85	$136.90
Purchase #4	$246.91	8.151%	$267.0356	$267.04	$267.05	$267.00
Purchase #5	$40.89	11.704%	$45.6758	$45.68	$45.70	$45.70
Purchase #6	$20.61	5.112%	$21.6636	$21.66	$21.65	$21.70
Purchase #7	$110.88	6.176%	$117.7279	$117.73	$117.75	$117.70
7 purchase totals =	$887.21		$972.2630	$972.27	$972.25	$972.30