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	$81.86	3.862%	$85.0214	$85.02	$85.00	$85.00
Purchase #2	$56.77	5.184%	$59.713	$59.71	$59.70	$59.70
Purchase #3	$45.44	6.404%	$48.35	$48.35	$48.35	$48.40
Purchase #4	$18.87	13.396%	$21.3978	$21.40	$21.40	$21.40
Purchase #5	$165.73	11.160%	$184.2255	$184.23	$184.25	$184.20
Purchase #6	$199.43	4.579%	$208.5619	$208.56	$208.55	$208.60
Purchase #7	$150.93	6.314%	$160.4597	$160.46	$160.45	$160.50
7 purchase totals =	$719.03		$767.7293	$767.73	$767.70	$767.80