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	$80.89	6.318%	$86.0006	$86.00	$86.00	$86.00
Purchase #2	$95.62	4.637%	$100.0539	$100.05	$100.05	$100.10
Purchase #3	$90.28	6.748%	$96.3721	$96.37	$96.35	$96.40
Purchase #4	$75.94	3.520%	$78.6131	$78.61	$78.60	$78.60
Purchase #5	$159.49	6.534%	$169.9111	$169.91	$169.90	$169.90
Purchase #6	$146.35	13.583%	$166.2287	$166.23	$166.25	$166.20
Purchase #7	$123.85	11.596%	$138.2116	$138.21	$138.20	$138.20
7 purchase totals =	$772.42		$835.3911	$835.38	$835.35	$835.40