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	$101.53	4.153%	$105.7465	$105.75	$105.75	$105.70
Purchase #2	$143.28	8.533%	$155.5061	$155.51	$155.50	$155.50
Purchase #3	$177.25	11.710%	$198.006	$198.01	$198.00	$198.00
Purchase #4	$56.82	4.449%	$59.3479	$59.35	$59.35	$59.30
Purchase #5	$211.68	13.672%	$240.6209	$240.62	$240.60	$240.60
Purchase #6	$76.36	3.153%	$78.7676	$78.77	$78.75	$78.80
Purchase #7	$77.93	9.520%	$85.3489	$85.35	$85.35	$85.30
7 purchase totals =	$844.85		$923.3439	$923.36	$923.30	$923.20