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	$57.36	6.591%	$61.1406	$61.14	$61.15	$61.10
Purchase #2	$249.98	5.508%	$263.7489	$263.75	$263.75	$263.70
Purchase #3	$53.83	4.747%	$56.3853	$56.39	$56.40	$56.40
Purchase #4	$46.66	13.404%	$52.9143	$52.91	$52.90	$52.90
Purchase #5	$60.86	8.520%	$66.0453	$66.05	$66.05	$66.00
Purchase #6	$34.32	4.714%	$35.9378	$35.94	$35.95	$35.90
Purchase #7	$85.32	11.678%	$95.2837	$95.28	$95.30	$95.30
7 purchase totals =	$588.33		$631.4559	$631.46	$631.50	$631.30