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	$77.90	13.526%	$88.4368	$88.44	$88.45	$88.40
Purchase #2	$36.93	3.574%	$38.2499	$38.25	$38.25	$38.20
Purchase #3	$9.84	4.320%	$10.2651	$10.27	$10.25	$10.30
Purchase #4	$42.42	4.872%	$44.4867	$44.49	$44.50	$44.50
Purchase #5	$57.81	3.611%	$59.8975	$59.90	$59.90	$59.90
Purchase #6	$195.41	13.117%	$221.0419	$221.04	$221.05	$221.00
Purchase #7	$20.86	9.204%	$22.78	$22.78	$22.80	$22.80
7 purchase totals =	$441.17		$485.1579	$485.17	$485.20	$485.10