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	$57.28	13.314%	$64.9063	$64.91	$64.90	$64.90
Purchase #2	$12.98	7.178%	$13.9117	$13.91	$13.90	$13.90
Purchase #3	$80.35	13.814%	$91.4495	$91.45	$91.45	$91.40
Purchase #4	$29.63	7.738%	$31.9228	$31.92	$31.90	$31.90
Purchase #5	$16.96	3.574%	$17.5662	$17.57	$17.55	$17.60
Purchase #6	$120.69	4.163%	$125.7143	$125.71	$125.70	$125.70
Purchase #7	$105.81	5.757%	$111.9015	$111.90	$111.90	$111.90
7 purchase totals =	$423.70		$457.3723	$457.37	$457.30	$457.30