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	$210.91	11.830%	$235.8607	$235.86	$235.85	$235.90
Purchase #2	$96.45	9.419%	$105.5346	$105.53	$105.55	$105.50
Purchase #3	$27.74	5.873%	$29.3692	$29.37	$29.35	$29.40
Purchase #4	$131.42	6.854%	$140.4275	$140.43	$140.45	$140.40
Purchase #5	$104.43	7.116%	$111.8612	$111.86	$111.85	$111.90
Purchase #6	$97.63	4.341%	$101.8681	$101.87	$101.85	$101.90
Purchase #7	$17.47	6.690%	$18.6387	$18.64	$18.65	$18.60
7 purchase totals =	$686.05		$743.5600	$743.56	$743.55	$743.60