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	$141.60	12.232%	$158.9205	$158.92	$158.90	$158.90
Purchase #2	$212.26	8.230%	$229.729	$229.73	$229.75	$229.70
Purchase #3	$44.94	13.484%	$50.9997	$51.00	$51.00	$51.00
Purchase #4	$165.64	13.779%	$188.4635	$188.46	$188.45	$188.50
Purchase #5	$115.97	3.333%	$119.8353	$119.84	$119.85	$119.80
Purchase #6	$240.34	6.337%	$255.5703	$255.57	$255.55	$255.60
Purchase #7	$11.76	6.173%	$12.4859	$12.49	$12.50	$12.50
7 purchase totals =	$932.51		$1,016.0042	$1,016.01	$1,016.00	$1,016.00