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	$216.46	9.354%	$236.7077	$236.71	$236.70	$236.70
Purchase #2	$29.35	10.287%	$32.3692	$32.37	$32.35	$32.40
Purchase #3	$166.94	7.553%	$179.549	$179.55	$179.55	$179.50
Purchase #4	$172.74	10.849%	$191.4806	$191.48	$191.50	$191.50
Purchase #5	$37.85	9.829%	$41.5703	$41.57	$41.55	$41.60
Purchase #6	$93.55	7.166%	$100.2538	$100.25	$100.25	$100.30
Purchase #7	$45.89	13.429%	$52.0526	$52.05	$52.05	$52.10
7 purchase totals =	$762.78		$833.9832	$833.98	$833.95	$834.10