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	$211.53	11.320%	$235.4752	$235.48	$235.50	$235.50
Purchase #2	$49.56	5.389%	$52.2308	$52.23	$52.25	$52.20
Purchase #3	$93.59	12.853%	$105.6191	$105.62	$105.60	$105.60
Purchase #4	$188.39	13.785%	$214.3596	$214.36	$214.35	$214.40
Purchase #5	$66.49	9.720%	$72.9528	$72.95	$72.95	$73.00
Purchase #6	$76.85	8.808%	$83.6189	$83.62	$83.60	$83.60
Purchase #7	$28.69	10.363%	$31.6631	$31.66	$31.65	$31.70
7 purchase totals =	$715.10		$795.9195	$795.92	$795.90	$796.00