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	$231.77	3.793%	$240.561	$240.56	$240.55	$240.60
Purchase #2	$10.70	6.523%	$11.398	$11.40	$11.40	$11.40
Purchase #3	$38.26	5.533%	$40.3769	$40.38	$40.40	$40.40
Purchase #4	$104.75	11.580%	$116.8801	$116.88	$116.90	$116.90
Purchase #5	$62.26	11.593%	$69.4778	$69.48	$69.50	$69.50
Purchase #6	$18.52	5.189%	$19.481	$19.48	$19.50	$19.50
Purchase #7	$94.93	4.645%	$99.3395	$99.34	$99.35	$99.30
7 purchase totals =	$561.19		$597.5143	$597.52	$597.60	$597.60