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	$183.87	12.281%	$206.4511	$206.45	$206.45	$206.50
Purchase #2	$247.52	11.221%	$275.2942	$275.29	$275.30	$275.30
Purchase #3	$144.75	12.420%	$162.728	$162.73	$162.75	$162.70
Purchase #4	$37.81	12.657%	$42.5956	$42.60	$42.60	$42.60
Purchase #5	$218.38	6.820%	$233.2735	$233.27	$233.25	$233.30
Purchase #6	$230.69	9.821%	$253.3461	$253.35	$253.35	$253.30
Purchase #7	$80.55	9.689%	$88.3545	$88.35	$88.35	$88.40
7 purchase totals =	$1,143.57		$1,262.0430	$1,262.04	$1,262.05	$1,262.10