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	$107.51	4.370%	$112.2082	$112.21	$112.20	$112.20
Purchase #2	$77.34	3.261%	$79.8621	$79.86	$79.85	$79.90
Purchase #3	$156.41	7.787%	$168.5896	$168.59	$168.60	$168.60
Purchase #4	$85.59	5.353%	$90.1716	$90.17	$90.15	$90.20
Purchase #5	$26.50	10.577%	$29.3029	$29.30	$29.30	$29.30
Purchase #6	$74.31	8.699%	$80.7742	$80.77	$80.75	$80.80
Purchase #7	$228.88	6.425%	$243.5855	$243.59	$243.60	$243.60
7 purchase totals =	$756.54		$804.4941	$804.49	$804.45	$804.60