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	$23.58	10.467%	$26.0481	$26.05	$26.05	$26.00
Purchase #2	$116.34	8.698%	$126.4593	$126.46	$126.45	$126.50
Purchase #3	$67.68	13.740%	$76.9792	$76.98	$77.00	$77.00
Purchase #4	$53.59	11.519%	$59.763	$59.76	$59.75	$59.80
Purchase #5	$171.49	10.385%	$189.2992	$189.30	$189.30	$189.30
Purchase #6	$71.56	9.543%	$78.389	$78.39	$78.40	$78.40
Purchase #7	$15.53	6.308%	$16.5096	$16.51	$16.50	$16.50
7 purchase totals =	$519.77		$573.4474	$573.45	$573.45	$573.50