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	$119.49	12.446%	$134.3617	$134.36	$134.35	$134.40
Purchase #2	$135.33	3.143%	$139.5834	$139.58	$139.60	$139.60
Purchase #3	$78.42	3.701%	$81.3223	$81.32	$81.30	$81.30
Purchase #4	$164.51	9.276%	$179.7699	$179.77	$179.75	$179.80
Purchase #5	$37.31	13.484%	$42.3409	$42.34	$42.35	$42.30
Purchase #6	$224.89	3.505%	$232.7724	$232.77	$232.75	$232.80
Purchase #7	$139.82	9.246%	$152.7478	$152.75	$152.75	$152.70
7 purchase totals =	$899.77		$962.8984	$962.89	$962.85	$962.90