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	$139.47	8.653%	$151.5383	$151.54	$151.55	$151.50
Purchase #2	$72.64	6.558%	$77.4037	$77.40	$77.40	$77.40
Purchase #3	$11.58	7.554%	$12.4548	$12.45	$12.45	$12.50
Purchase #4	$116.93	12.394%	$131.4223	$131.42	$131.40	$131.40
Purchase #5	$250.89	13.390%	$284.4842	$284.48	$284.50	$284.50
Purchase #6	$211.51	8.256%	$228.9723	$228.97	$228.95	$229.00
Purchase #7	$82.80	7.640%	$89.1259	$89.13	$89.15	$89.10
7 purchase totals =	$885.82		$975.4015	$975.39	$975.40	$975.40