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	$191.40	8.349%	$207.38	$207.38	$207.40	$207.40
Purchase #2	$114.77	7.442%	$123.3112	$123.31	$123.30	$123.30
Purchase #3	$29.37	10.387%	$32.4207	$32.42	$32.40	$32.40
Purchase #4	$126.95	11.190%	$141.1557	$141.16	$141.15	$141.20
Purchase #5	$151.52	6.851%	$161.9006	$161.90	$161.90	$161.90
Purchase #6	$144.67	5.581%	$152.744	$152.74	$152.75	$152.70
Purchase #7	$111.86	10.641%	$123.763	$123.76	$123.75	$123.80
7 purchase totals =	$870.54		$942.6752	$942.67	$942.65	$942.70