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	$99.57	6.310%	$105.8529	$105.85	$105.85	$105.90
Purchase #2	$208.51	7.869%	$224.9177	$224.92	$224.90	$224.90
Purchase #3	$135.93	12.423%	$152.8166	$152.82	$152.80	$152.80
Purchase #4	$48.78	4.495%	$50.9727	$50.97	$50.95	$51.00
Purchase #5	$232.70	3.528%	$240.9097	$240.91	$240.90	$240.90
Purchase #6	$186.59	12.849%	$210.5649	$210.56	$210.55	$210.60
Purchase #7	$70.74	9.730%	$77.623	$77.62	$77.60	$77.60
7 purchase totals =	$982.82		$1,063.6575	$1,063.65	$1,063.55	$1,063.70