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	$100.54	8.863%	$109.4509	$109.45	$109.45	$109.50
Purchase #2	$195.28	10.792%	$216.3546	$216.35	$216.35	$216.40
Purchase #3	$37.72	11.421%	$42.028	$42.03	$42.05	$42.00
Purchase #4	$217.61	11.717%	$243.1074	$243.11	$243.10	$243.10
Purchase #5	$184.31	11.309%	$205.1536	$205.15	$205.15	$205.20
Purchase #6	$104.60	12.366%	$117.5348	$117.53	$117.55	$117.50
Purchase #7	$165.27	13.445%	$187.4906	$187.49	$187.50	$187.50
7 purchase totals =	$1,005.33		$1,121.1199	$1,121.11	$1,121.15	$1,121.20