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	$87.39	7.537%	$93.9766	$93.98	$94.00	$94.00
Purchase #2	$95.68	7.467%	$102.8244	$102.82	$102.80	$102.80
Purchase #3	$94.93	13.267%	$107.5244	$107.52	$107.50	$107.50
Purchase #4	$31.60	4.117%	$32.901	$32.90	$32.90	$32.90
Purchase #5	$54.89	12.751%	$61.889	$61.89	$61.90	$61.90
Purchase #6	$17.89	3.261%	$18.4734	$18.47	$18.45	$18.50
Purchase #7	$163.41	9.591%	$179.0827	$179.08	$179.10	$179.10
7 purchase totals =	$545.79		$596.6715	$596.66	$596.65	$596.70