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	$221.41	5.765%	$234.1743	$234.17	$234.15	$234.20
Purchase #2	$205.60	12.498%	$231.2959	$231.30	$231.30	$231.30
Purchase #3	$106.88	13.574%	$121.3879	$121.39	$121.40	$121.40
Purchase #4	$93.30	4.285%	$97.2979	$97.30	$97.30	$97.30
Purchase #5	$42.28	9.739%	$46.3976	$46.40	$46.40	$46.40
Purchase #6	$119.85	12.540%	$134.8792	$134.88	$134.90	$134.90
Purchase #7	$131.85	3.817%	$136.8827	$136.88	$136.90	$136.90
7 purchase totals =	$921.17		$1,002.3155	$1,002.32	$1,002.35	$1,002.40