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	$153.29	12.476%	$172.4145	$172.41	$172.40	$172.40
Purchase #2	$159.31	4.534%	$166.5331	$166.53	$166.55	$166.50
Purchase #3	$223.63	9.254%	$244.3247	$244.32	$244.30	$244.30
Purchase #4	$16.40	13.539%	$18.6204	$18.62	$18.60	$18.60
Purchase #5	$232.52	3.837%	$241.4418	$241.44	$241.45	$241.40
Purchase #6	$182.35	7.826%	$196.6207	$196.62	$196.60	$196.60
Purchase #7	$228.48	11.260%	$254.2068	$254.21	$254.20	$254.20
7 purchase totals =	$1,195.98		$1,294.1620	$1,294.15	$1,294.10	$1,294.00