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	$47.55	4.579%	$49.7273	$49.73	$49.75	$49.70
Purchase #2	$178.71	5.728%	$188.9465	$188.95	$188.95	$188.90
Purchase #3	$144.66	12.182%	$162.2825	$162.28	$162.30	$162.30
Purchase #4	$46.67	13.204%	$52.8323	$52.83	$52.85	$52.80
Purchase #5	$248.52	4.508%	$259.7233	$259.72	$259.70	$259.70
Purchase #6	$37.53	12.520%	$42.2288	$42.23	$42.25	$42.20
Purchase #7	$125.79	12.703%	$141.7691	$141.77	$141.75	$141.80
7 purchase totals =	$829.43		$897.5098	$897.51	$897.55	$897.40