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	$230.29	10.845%	$255.265	$255.27	$255.25	$255.30
Purchase #2	$126.83	9.702%	$139.135	$139.14	$139.15	$139.10
Purchase #3	$153.31	9.150%	$167.3379	$167.34	$167.35	$167.30
Purchase #4	$55.52	11.212%	$61.7449	$61.74	$61.75	$61.70
Purchase #5	$65.29	11.325%	$72.6841	$72.68	$72.70	$72.70
Purchase #6	$222.33	9.406%	$243.2424	$243.24	$243.25	$243.20
Purchase #7	$250.86	6.859%	$268.0665	$268.07	$268.05	$268.10
7 purchase totals =	$1,104.43		$1,207.4758	$1,207.48	$1,207.50	$1,207.40