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	$64.71	4.287%	$67.4841	$67.48	$67.50	$67.50
Purchase #2	$160.28	4.348%	$167.249	$167.25	$167.25	$167.20
Purchase #3	$18.60	13.596%	$21.1289	$21.13	$21.15	$21.10
Purchase #4	$41.39	11.152%	$46.0058	$46.01	$46.00	$46.00
Purchase #5	$50.94	12.460%	$57.2871	$57.29	$57.30	$57.30
Purchase #6	$245.91	10.107%	$270.7641	$270.76	$270.75	$270.80
Purchase #7	$158.78	9.429%	$173.7514	$173.75	$173.75	$173.80
7 purchase totals =	$740.61		$803.6704	$803.67	$803.70	$803.70