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	$127.61	10.756%	$141.3357	$141.34	$141.35	$141.30
Purchase #2	$185.96	10.179%	$204.8889	$204.89	$204.90	$204.90
Purchase #3	$106.49	6.662%	$113.5844	$113.58	$113.60	$113.60
Purchase #4	$50.39	4.313%	$52.5633	$52.56	$52.55	$52.60
Purchase #5	$54.90	11.668%	$61.3057	$61.31	$61.30	$61.30
Purchase #6	$141.43	7.725%	$152.3555	$152.36	$152.35	$152.40
Purchase #7	$207.94	9.561%	$227.8211	$227.82	$227.80	$227.80
7 purchase totals =	$874.72		$953.8546	$953.86	$953.85	$953.90