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	$247.69	3.637%	$256.6985	$256.70	$256.70	$256.70
Purchase #2	$201.83	10.829%	$223.6862	$223.69	$223.70	$223.70
Purchase #3	$236.85	8.197%	$256.2646	$256.26	$256.25	$256.30
Purchase #4	$12.35	10.153%	$13.6039	$13.60	$13.60	$13.60
Purchase #5	$146.87	12.172%	$164.747	$164.75	$164.75	$164.70
Purchase #6	$96.59	13.749%	$109.8702	$109.87	$109.85	$109.90
Purchase #7	$211.37	12.274%	$237.3136	$237.31	$237.30	$237.30
7 purchase totals =	$1,153.55		$1,262.1840	$1,262.18	$1,262.15	$1,262.20