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	$32.86	7.329%	$35.2683	$35.27	$35.25	$35.30
Purchase #2	$15.65	12.543%	$17.613	$17.61	$17.60	$17.60
Purchase #3	$50.46	8.230%	$54.6129	$54.61	$54.60	$54.60
Purchase #4	$133.93	8.637%	$145.4975	$145.50	$145.50	$145.50
Purchase #5	$94.42	12.106%	$105.8505	$105.85	$105.85	$105.90
Purchase #6	$243.86	12.872%	$275.2497	$275.25	$275.25	$275.20
Purchase #7	$24.27	5.636%	$25.6379	$25.64	$25.65	$25.60
7 purchase totals =	$595.45		$659.7298	$659.73	$659.70	$659.70