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	$93.86	3.504%	$97.1489	$97.15	$97.15	$97.10
Purchase #2	$141.88	3.119%	$146.3052	$146.31	$146.30	$146.30
Purchase #3	$242.72	5.308%	$255.6036	$255.60	$255.60	$255.60
Purchase #4	$16.37	4.598%	$17.1227	$17.12	$17.10	$17.10
Purchase #5	$42.93	7.374%	$46.0957	$46.10	$46.10	$46.10
Purchase #6	$89.59	11.619%	$99.9995	$100.00	$100.00	$100.00
Purchase #7	$112.26	13.649%	$127.5824	$127.58	$127.60	$127.60
7 purchase totals =	$739.61		$789.8580	$789.86	$789.85	$789.80