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	$104.35	7.858%	$112.5498	$112.55	$112.55	$112.50
Purchase #2	$6.59	7.311%	$7.0718	$7.07	$7.05	$7.10
Purchase #3	$170.40	12.613%	$191.8926	$191.89	$191.90	$191.90
Purchase #4	$157.56	6.421%	$167.6769	$167.68	$167.70	$167.70
Purchase #5	$109.68	12.347%	$123.2222	$123.22	$123.20	$123.20
Purchase #6	$222.60	7.211%	$238.6517	$238.65	$238.65	$238.70
Purchase #7	$124.84	10.127%	$137.4825	$137.48	$137.50	$137.50
7 purchase totals =	$896.02		$978.5475	$978.54	$978.55	$978.60