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	$65.80	9.492%	$72.0457	$72.05	$72.05	$72.00
Purchase #2	$59.39	12.588%	$66.866	$66.87	$66.85	$66.90
Purchase #3	$239.62	5.804%	$253.5275	$253.53	$253.55	$253.50
Purchase #4	$247.29	9.436%	$270.6243	$270.62	$270.60	$270.60
Purchase #5	$184.45	11.303%	$205.2984	$205.30	$205.30	$205.30
Purchase #6	$170.53	8.713%	$185.3883	$185.39	$185.40	$185.40
Purchase #7	$212.77	7.672%	$229.0937	$229.09	$229.10	$229.10
7 purchase totals =	$1,179.85		$1,282.8439	$1,282.85	$1,282.85	$1,282.80