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	$149.80	12.535%	$168.5774	$168.58	$168.60	$168.60
Purchase #2	$81.87	12.329%	$91.9638	$91.96	$91.95	$92.00
Purchase #3	$95.99	4.411%	$100.2241	$100.22	$100.20	$100.20
Purchase #4	$93.48	8.401%	$101.3333	$101.33	$101.35	$101.30
Purchase #5	$111.25	4.866%	$116.6634	$116.66	$116.65	$116.70
Purchase #6	$145.73	10.699%	$161.3217	$161.32	$161.30	$161.30
Purchase #7	$100.89	4.532%	$105.4623	$105.46	$105.45	$105.50
7 purchase totals =	$779.01		$845.5460	$845.53	$845.50	$845.60