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	$66.29	5.760%	$70.1083	$70.11	$70.10	$70.10
Purchase #2	$113.90	5.792%	$120.4971	$120.50	$120.50	$120.50
Purchase #3	$34.85	8.813%	$37.9213	$37.92	$37.90	$37.90
Purchase #4	$164.84	8.275%	$178.4805	$178.48	$178.50	$178.50
Purchase #5	$238.72	6.330%	$253.831	$253.83	$253.85	$253.80
Purchase #6	$186.37	6.833%	$199.1047	$199.10	$199.10	$199.10
Purchase #7	$48.59	11.513%	$54.1842	$54.18	$54.20	$54.20
7 purchase totals =	$853.56		$914.1271	$914.12	$914.15	$914.10