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	$116.32	12.671%	$131.0589	$131.06	$131.05	$131.10
Purchase #2	$8.26	4.304%	$8.6155	$8.62	$8.60	$8.60
Purchase #3	$113.57	5.503%	$119.8198	$119.82	$119.80	$119.80
Purchase #4	$33.54	11.296%	$37.3287	$37.33	$37.35	$37.30
Purchase #5	$119.89	3.174%	$123.6953	$123.70	$123.70	$123.70
Purchase #6	$104.84	13.610%	$119.1087	$119.11	$119.10	$119.10
Purchase #7	$161.51	11.603%	$180.25	$180.25	$180.25	$180.30
7 purchase totals =	$657.93		$719.8769	$719.89	$719.85	$719.90