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	$53.35	5.285%	$56.1695	$56.17	$56.15	$56.20
Purchase #2	$60.51	4.578%	$63.2801	$63.28	$63.30	$63.30
Purchase #3	$51.83	6.694%	$55.2995	$55.30	$55.30	$55.30
Purchase #4	$232.37	10.128%	$255.9044	$255.90	$255.90	$255.90
Purchase #5	$124.59	10.656%	$137.8663	$137.87	$137.85	$137.90
Purchase #6	$226.77	9.775%	$248.9368	$248.94	$248.95	$248.90
Purchase #7	$229.30	6.267%	$243.6702	$243.67	$243.65	$243.70
7 purchase totals =	$978.72		$1,061.1268	$1,061.13	$1,061.10	$1,061.20