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	$83.28	3.478%	$86.1765	$86.18	$86.20	$86.20
Purchase #2	$84.87	5.786%	$89.7806	$89.78	$89.80	$89.80
Purchase #3	$248.80	11.255%	$276.8024	$276.80	$276.80	$276.80
Purchase #4	$176.45	10.666%	$195.2702	$195.27	$195.25	$195.30
Purchase #5	$105.48	6.493%	$112.3288	$112.33	$112.35	$112.30
Purchase #6	$126.38	3.113%	$130.3142	$130.31	$130.30	$130.30
Purchase #7	$228.80	10.679%	$253.2336	$253.23	$253.25	$253.20
7 purchase totals =	$1,054.06		$1,143.9063	$1,143.90	$1,143.95	$1,143.90