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	$56.50	5.229%	$59.4544	$59.45	$59.45	$59.50
Purchase #2	$102.73	13.156%	$116.2452	$116.25	$116.25	$116.20
Purchase #3	$44.70	5.811%	$47.2975	$47.30	$47.30	$47.30
Purchase #4	$45.45	11.816%	$50.8204	$50.82	$50.80	$50.80
Purchase #5	$83.55	8.686%	$90.8072	$90.81	$90.80	$90.80
Purchase #6	$15.74	6.382%	$16.7445	$16.74	$16.75	$16.70
Purchase #7	$61.99	13.544%	$70.3859	$70.39	$70.40	$70.40
7 purchase totals =	$410.66		$451.7551	$451.76	$451.75	$451.70