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	$212.38	10.254%	$234.1574	$234.16	$234.15	$234.20
Purchase #2	$123.38	10.506%	$136.3423	$136.34	$136.35	$136.30
Purchase #3	$128.45	13.841%	$146.2288	$146.23	$146.25	$146.20
Purchase #4	$164.84	4.776%	$172.7128	$172.71	$172.70	$172.70
Purchase #5	$55.59	13.364%	$63.019	$63.02	$63.00	$63.00
Purchase #6	$108.84	13.429%	$123.4561	$123.46	$123.45	$123.50
Purchase #7	$127.74	11.312%	$142.1899	$142.19	$142.20	$142.20
7 purchase totals =	$921.22		$1,018.1063	$1,018.11	$1,018.10	$1,018.10