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	$177.26	4.850%	$185.8571	$185.86	$185.85	$185.90
Purchase #2	$195.31	10.175%	$215.1828	$215.18	$215.20	$215.20
Purchase #3	$246.77	13.347%	$279.7064	$279.71	$279.70	$279.70
Purchase #4	$61.25	8.722%	$66.5922	$66.59	$66.60	$66.60
Purchase #5	$222.95	10.140%	$245.5571	$245.56	$245.55	$245.60
Purchase #6	$127.96	12.837%	$144.3862	$144.39	$144.40	$144.40
Purchase #7	$142.55	12.559%	$160.4529	$160.45	$160.45	$160.50
7 purchase totals =	$1,174.05		$1,297.7347	$1,297.74	$1,297.75	$1,297.90