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	$61.67	5.657%	$65.1587	$65.16	$65.15	$65.20
Purchase #2	$216.72	5.261%	$228.1216	$228.12	$228.10	$228.10
Purchase #3	$209.40	11.358%	$233.1837	$233.18	$233.20	$233.20
Purchase #4	$18.64	7.515%	$20.0408	$20.04	$20.05	$20.00
Purchase #5	$82.88	13.620%	$94.1683	$94.17	$94.15	$94.20
Purchase #6	$38.78	4.515%	$40.5309	$40.53	$40.55	$40.50
Purchase #7	$102.65	9.254%	$112.1492	$112.15	$112.15	$112.10
7 purchase totals =	$730.74		$793.3532	$793.35	$793.35	$793.30