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	$117.55	12.729%	$132.5129	$132.51	$132.50	$132.50
Purchase #2	$152.97	3.446%	$158.2413	$158.24	$158.25	$158.20
Purchase #3	$7.77	3.670%	$8.0552	$8.06	$8.05	$8.10
Purchase #4	$134.98	8.804%	$146.8636	$146.86	$146.85	$146.90
Purchase #5	$78.34	9.147%	$85.5058	$85.51	$85.50	$85.50
Purchase #6	$44.93	13.396%	$50.9488	$50.95	$50.95	$50.90
Purchase #7	$195.74	13.832%	$222.8148	$222.81	$222.80	$222.80
7 purchase totals =	$732.28		$804.9424	$804.94	$804.90	$804.90