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	$217.26	4.862%	$227.8232	$227.82	$227.80	$227.80
Purchase #2	$128.85	6.846%	$137.6711	$137.67	$137.65	$137.70
Purchase #3	$218.50	13.392%	$247.7615	$247.76	$247.75	$247.80
Purchase #4	$151.66	4.496%	$158.4786	$158.48	$158.50	$158.50
Purchase #5	$87.78	5.193%	$92.3384	$92.34	$92.35	$92.30
Purchase #6	$64.33	13.264%	$72.8627	$72.86	$72.85	$72.90
Purchase #7	$148.78	6.500%	$158.4507	$158.45	$158.45	$158.50
7 purchase totals =	$1,017.16		$1,095.3862	$1,095.38	$1,095.35	$1,095.50