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	$141.63	3.689%	$146.8547	$146.85	$146.85	$146.90
Purchase #2	$126.54	4.521%	$132.2609	$132.26	$132.25	$132.30
Purchase #3	$93.41	11.404%	$104.0625	$104.06	$104.05	$104.10
Purchase #4	$21.99	11.444%	$24.5065	$24.51	$24.50	$24.50
Purchase #5	$229.36	11.436%	$255.5896	$255.59	$255.60	$255.60
Purchase #6	$140.37	3.681%	$145.537	$145.54	$145.55	$145.50
Purchase #7	$145.83	12.820%	$164.5254	$164.53	$164.55	$164.50
7 purchase totals =	$899.13		$973.3366	$973.34	$973.35	$973.40