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	$233.25	4.104%	$242.8226	$242.82	$242.80	$242.80
Purchase #2	$244.38	4.548%	$255.4944	$255.49	$255.50	$255.50
Purchase #3	$18.92	13.740%	$21.5196	$21.52	$21.50	$21.50
Purchase #4	$227.30	10.648%	$251.5029	$251.50	$251.50	$251.50
Purchase #5	$112.41	11.131%	$124.9224	$124.92	$124.90	$124.90
Purchase #6	$109.69	4.784%	$114.9376	$114.94	$114.95	$114.90
Purchase #7	$117.33	8.266%	$127.0285	$127.03	$127.05	$127.00
7 purchase totals =	$1,063.28		$1,138.2280	$1,138.22	$1,138.20	$1,138.10