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	$189.89	13.196%	$214.9479	$214.95	$214.95	$214.90
Purchase #2	$54.37	13.256%	$61.5773	$61.58	$61.60	$61.60
Purchase #3	$25.93	7.387%	$27.8454	$27.85	$27.85	$27.80
Purchase #4	$166.27	10.122%	$183.0998	$183.10	$183.10	$183.10
Purchase #5	$248.96	11.796%	$278.3273	$278.33	$278.35	$278.30
Purchase #6	$75.57	9.300%	$82.598	$82.60	$82.60	$82.60
Purchase #7	$126.78	10.680%	$140.3201	$140.32	$140.30	$140.30
7 purchase totals =	$887.77		$988.7158	$988.73	$988.75	$988.60