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	$173.36	10.831%	$192.1366	$192.14	$192.15	$192.10
Purchase #2	$45.29	12.470%	$50.9377	$50.94	$50.95	$50.90
Purchase #3	$154.81	12.329%	$173.8965	$173.90	$173.90	$173.90
Purchase #4	$209.31	3.330%	$216.28	$216.28	$216.30	$216.30
Purchase #5	$111.36	10.485%	$123.0361	$123.04	$123.05	$123.00
Purchase #6	$85.26	6.696%	$90.969	$90.97	$90.95	$91.00
Purchase #7	$13.55	5.235%	$14.2593	$14.26	$14.25	$14.30
7 purchase totals =	$792.94		$861.5152	$861.53	$861.55	$861.50