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	$213.35	6.562%	$227.35	$227.35	$227.35	$227.40
Purchase #2	$71.53	4.258%	$74.5757	$74.58	$74.60	$74.60
Purchase #3	$34.81	12.822%	$39.2733	$39.27	$39.25	$39.30
Purchase #4	$82.29	11.650%	$91.8768	$91.88	$91.90	$91.90
Purchase #5	$56.77	10.859%	$62.9347	$62.93	$62.95	$62.90
Purchase #6	$107.89	11.490%	$120.2866	$120.29	$120.30	$120.30
Purchase #7	$162.50	13.383%	$184.2474	$184.25	$184.25	$184.20
7 purchase totals =	$729.14		$800.5445	$800.55	$800.60	$800.60