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	$31.77	4.333%	$33.1466	$33.15	$33.15	$33.10
Purchase #2	$50.59	5.604%	$53.4251	$53.43	$53.45	$53.40
Purchase #3	$245.54	4.304%	$256.108	$256.11	$256.10	$256.10
Purchase #4	$88.62	13.574%	$100.6493	$100.65	$100.65	$100.60
Purchase #5	$65.59	6.333%	$69.7438	$69.74	$69.75	$69.70
Purchase #6	$157.60	8.460%	$170.933	$170.93	$170.95	$170.90
Purchase #7	$21.85	10.341%	$24.1095	$24.11	$24.10	$24.10
7 purchase totals =	$661.56		$708.1153	$708.12	$708.15	$707.90