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	$82.40	3.629%	$85.3903	$85.39	$85.40	$85.40
Purchase #2	$54.69	7.688%	$58.8946	$58.89	$58.90	$58.90
Purchase #3	$201.98	5.129%	$212.3396	$212.34	$212.35	$212.30
Purchase #4	$19.50	10.707%	$21.5879	$21.59	$21.60	$21.60
Purchase #5	$140.58	12.134%	$157.638	$157.64	$157.65	$157.60
Purchase #6	$173.49	6.851%	$185.3758	$185.38	$185.40	$185.40
Purchase #7	$97.78	8.229%	$105.8263	$105.83	$105.85	$105.80
7 purchase totals =	$770.42		$827.0525	$827.06	$827.15	$827.00