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	$116.85	5.694%	$123.5034	$123.50	$123.50	$123.50
Purchase #2	$244.93	7.335%	$262.8956	$262.90	$262.90	$262.90
Purchase #3	$134.29	13.216%	$152.0378	$152.04	$152.05	$152.00
Purchase #4	$220.69	10.201%	$243.2026	$243.20	$243.20	$243.20
Purchase #5	$203.83	9.744%	$223.6912	$223.69	$223.70	$223.70
Purchase #6	$43.50	13.800%	$49.503	$49.50	$49.50	$49.50
Purchase #7	$146.95	4.435%	$153.4672	$153.47	$153.45	$153.50
7 purchase totals =	$1,111.04		$1,208.3008	$1,208.30	$1,208.30	$1,208.30