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	$127.34	3.855%	$132.249	$132.25	$132.25	$132.20
Purchase #2	$137.53	10.822%	$152.4135	$152.41	$152.40	$152.40
Purchase #3	$224.81	5.690%	$237.6017	$237.60	$237.60	$237.60
Purchase #4	$117.51	5.713%	$124.2233	$124.22	$124.20	$124.20
Purchase #5	$139.76	8.315%	$151.381	$151.38	$151.40	$151.40
Purchase #6	$90.31	3.521%	$93.4898	$93.49	$93.50	$93.50
Purchase #7	$174.50	4.870%	$182.9982	$183.00	$183.00	$183.00
7 purchase totals =	$1,011.76		$1,074.3565	$1,074.35	$1,074.35	$1,074.30