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	$93.79	8.182%	$101.4639	$101.46	$101.45	$101.50
Purchase #2	$182.60	3.203%	$188.4487	$188.45	$188.45	$188.40
Purchase #3	$196.34	12.695%	$221.2654	$221.27	$221.25	$221.30
Purchase #4	$94.88	11.228%	$105.5331	$105.53	$105.55	$105.50
Purchase #5	$53.37	5.247%	$56.1703	$56.17	$56.15	$56.20
Purchase #6	$44.92	7.192%	$48.1506	$48.15	$48.15	$48.20
Purchase #7	$38.87	8.762%	$42.2758	$42.28	$42.30	$42.30
7 purchase totals =	$704.77		$763.3078	$763.31	$763.30	$763.40