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	$53.83	10.342%	$59.3971	$59.40	$59.40	$59.40
Purchase #2	$20.26	12.573%	$22.8073	$22.81	$22.80	$22.80
Purchase #3	$205.96	4.527%	$215.2838	$215.28	$215.30	$215.30
Purchase #4	$84.85	9.637%	$93.027	$93.03	$93.05	$93.00
Purchase #5	$168.67	9.778%	$185.1626	$185.16	$185.15	$185.20
Purchase #6	$49.69	11.365%	$55.3373	$55.34	$55.35	$55.30
Purchase #7	$100.45	4.775%	$105.2465	$105.25	$105.25	$105.20
7 purchase totals =	$683.71		$736.2616	$736.27	$736.30	$736.20