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	$172.45	11.524%	$192.3231	$192.32	$192.30	$192.30
Purchase #2	$32.65	3.272%	$33.7183	$33.72	$33.70	$33.70
Purchase #3	$117.38	8.406%	$127.247	$127.25	$127.25	$127.20
Purchase #4	$132.89	5.235%	$139.8468	$139.85	$139.85	$139.80
Purchase #5	$37.56	12.663%	$42.3162	$42.32	$42.30	$42.30
Purchase #6	$72.68	4.547%	$75.9848	$75.98	$76.00	$76.00
Purchase #7	$16.78	5.403%	$17.6866	$17.69	$17.70	$17.70
7 purchase totals =	$582.39		$629.1228	$629.13	$629.10	$629.00