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	$32.48	10.527%	$35.8992	$35.90	$35.90	$35.90
Purchase #2	$94.60	4.740%	$99.084	$99.08	$99.10	$99.10
Purchase #3	$136.79	6.468%	$145.6376	$145.64	$145.65	$145.60
Purchase #4	$42.36	4.564%	$44.2933	$44.29	$44.30	$44.30
Purchase #5	$199.68	8.553%	$216.7586	$216.76	$216.75	$216.80
Purchase #6	$40.85	11.286%	$45.4603	$45.46	$45.45	$45.50
Purchase #7	$191.58	7.676%	$206.2857	$206.29	$206.30	$206.30
7 purchase totals =	$738.34		$793.4187	$793.42	$793.45	$793.50