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	$244.39	11.485%	$272.4582	$272.46	$272.45	$272.50
Purchase #2	$107.61	12.409%	$120.9633	$120.96	$120.95	$121.00
Purchase #3	$56.92	5.399%	$59.9931	$59.99	$60.00	$60.00
Purchase #4	$211.61	12.863%	$238.8294	$238.83	$238.85	$238.80
Purchase #5	$117.88	10.665%	$130.4519	$130.45	$130.45	$130.50
Purchase #6	$94.83	3.340%	$97.9973	$98.00	$98.00	$98.00
Purchase #7	$95.54	9.602%	$104.7138	$104.71	$104.70	$104.70
7 purchase totals =	$928.78		$1,025.4070	$1,025.40	$1,025.40	$1,025.50