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	$64.25	12.541%	$72.3076	$72.31	$72.30	$72.30
Purchase #2	$127.47	9.533%	$139.6217	$139.62	$139.60	$139.60
Purchase #3	$45.78	6.195%	$48.6161	$48.62	$48.60	$48.60
Purchase #4	$194.54	3.312%	$200.9832	$200.98	$201.00	$201.00
Purchase #5	$211.91	13.701%	$240.9438	$240.94	$240.95	$240.90
Purchase #6	$123.93	6.732%	$132.273	$132.27	$132.25	$132.30
Purchase #7	$24.83	13.276%	$28.1264	$28.13	$28.15	$28.10
7 purchase totals =	$792.71		$862.8718	$862.87	$862.85	$862.80