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	$181.72	12.569%	$204.5604	$204.56	$204.55	$204.60
Purchase #2	$229.25	13.151%	$259.3987	$259.40	$259.40	$259.40
Purchase #3	$36.29	4.418%	$37.8933	$37.89	$37.90	$37.90
Purchase #4	$77.60	13.729%	$88.2537	$88.25	$88.25	$88.30
Purchase #5	$16.93	8.588%	$18.3839	$18.38	$18.40	$18.40
Purchase #6	$88.36	9.850%	$97.0635	$97.06	$97.05	$97.10
Purchase #7	$155.40	11.198%	$172.8017	$172.80	$172.80	$172.80
7 purchase totals =	$785.55		$878.3552	$878.34	$878.35	$878.50