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	$58.86	12.203%	$66.0427	$66.04	$66.05	$66.00
Purchase #2	$209.38	7.284%	$224.6312	$224.63	$224.65	$224.60
Purchase #3	$116.39	11.658%	$129.9587	$129.96	$129.95	$130.00
Purchase #4	$118.42	11.141%	$131.6132	$131.61	$131.60	$131.60
Purchase #5	$215.85	4.286%	$225.1013	$225.10	$225.10	$225.10
Purchase #6	$72.73	12.810%	$82.0467	$82.05	$82.05	$82.00
Purchase #7	$10.76	12.757%	$12.1327	$12.13	$12.15	$12.10
7 purchase totals =	$802.39		$871.5265	$871.52	$871.55	$871.40