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	$26.74	4.575%	$27.9634	$27.96	$27.95	$28.00
Purchase #2	$45.74	10.572%	$50.5756	$50.58	$50.60	$50.60
Purchase #3	$102.72	3.661%	$106.4806	$106.48	$106.50	$106.50
Purchase #4	$82.45	4.655%	$86.288	$86.29	$86.30	$86.30
Purchase #5	$177.65	10.738%	$196.7261	$196.73	$196.75	$196.70
Purchase #6	$93.56	7.370%	$100.4554	$100.46	$100.45	$100.50
Purchase #7	$133.62	11.116%	$148.4732	$148.47	$148.45	$148.50
7 purchase totals =	$662.48		$716.9623	$716.97	$717.00	$717.10