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	$152.81	12.648%	$172.1374	$172.14	$172.15	$172.10
Purchase #2	$141.75	4.434%	$148.0352	$148.04	$148.05	$148.00
Purchase #3	$50.73	10.245%	$55.9273	$55.93	$55.95	$55.90
Purchase #4	$93.90	4.851%	$98.4551	$98.46	$98.45	$98.50
Purchase #5	$131.95	10.422%	$145.7018	$145.70	$145.70	$145.70
Purchase #6	$85.90	10.440%	$94.868	$94.87	$94.85	$94.90
Purchase #7	$33.56	13.523%	$38.0983	$38.10	$38.10	$38.10
7 purchase totals =	$690.60		$753.2231	$753.24	$753.25	$753.20