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	$180.77	8.594%	$196.3054	$196.31	$196.30	$196.30
Purchase #2	$27.94	7.772%	$30.1115	$30.11	$30.10	$30.10
Purchase #3	$90.32	10.715%	$99.9978	$100.00	$100.00	$100.00
Purchase #4	$66.35	7.227%	$71.1451	$71.15	$71.15	$71.10
Purchase #5	$120.50	3.861%	$125.1525	$125.15	$125.15	$125.20
Purchase #6	$112.81	11.229%	$125.4774	$125.48	$125.50	$125.50
Purchase #7	$205.86	3.262%	$212.5752	$212.58	$212.60	$212.60
7 purchase totals =	$804.55		$860.7649	$860.78	$860.80	$860.80