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	$83.45	12.671%	$94.0239	$94.02	$94.00	$94.00
Purchase #2	$93.57	7.202%	$100.3089	$100.31	$100.30	$100.30
Purchase #3	$56.46	10.561%	$62.4227	$62.42	$62.40	$62.40
Purchase #4	$206.78	7.664%	$222.6276	$222.63	$222.65	$222.60
Purchase #5	$123.37	8.604%	$133.9848	$133.98	$134.00	$134.00
Purchase #6	$140.25	8.792%	$152.5808	$152.58	$152.60	$152.60
Purchase #7	$197.73	7.249%	$212.0634	$212.06	$212.05	$212.10
7 purchase totals =	$901.61		$978.0121	$978.00	$978.00	$978.00