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	$207.43	4.397%	$216.5507	$216.55	$216.55	$216.60
Purchase #2	$29.39	13.244%	$33.2824	$33.28	$33.30	$33.30
Purchase #3	$164.77	3.591%	$170.6869	$170.69	$170.70	$170.70
Purchase #4	$33.70	12.295%	$37.8434	$37.84	$37.85	$37.80
Purchase #5	$191.90	12.420%	$215.734	$215.73	$215.75	$215.70
Purchase #6	$39.72	7.395%	$42.6573	$42.66	$42.65	$42.70
Purchase #7	$26.60	4.490%	$27.7943	$27.79	$27.80	$27.80
7 purchase totals =	$693.51		$744.5490	$744.54	$744.60	$744.60