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	$28.82	13.614%	$32.7436	$32.74	$32.75	$32.70
Purchase #2	$148.66	9.562%	$162.8749	$162.87	$162.85	$162.90
Purchase #3	$37.76	13.374%	$42.81	$42.81	$42.80	$42.80
Purchase #4	$220.85	6.846%	$235.9694	$235.97	$235.95	$236.00
Purchase #5	$185.96	13.784%	$211.5927	$211.59	$211.60	$211.60
Purchase #6	$33.80	3.733%	$35.0618	$35.06	$35.05	$35.10
Purchase #7	$207.97	11.324%	$231.5205	$231.52	$231.50	$231.50
7 purchase totals =	$863.82		$952.5729	$952.56	$952.50	$952.60