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	$75.86	10.528%	$83.8465	$83.85	$83.85	$83.80
Purchase #2	$125.89	9.261%	$137.5487	$137.55	$137.55	$137.50
Purchase #3	$16.33	10.244%	$18.0028	$18.00	$18.00	$18.00
Purchase #4	$82.88	10.740%	$91.7813	$91.78	$91.80	$91.80
Purchase #5	$73.95	12.164%	$82.9453	$82.95	$82.95	$82.90
Purchase #6	$142.76	5.873%	$151.1443	$151.14	$151.15	$151.10
Purchase #7	$167.89	13.522%	$190.5921	$190.59	$190.60	$190.60
7 purchase totals =	$685.56		$755.8610	$755.86	$755.90	$755.70