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	$31.63	8.540%	$34.3312	$34.33	$34.35	$34.30
Purchase #2	$216.92	8.639%	$235.6597	$235.66	$235.65	$235.70
Purchase #3	$54.25	9.121%	$59.1981	$59.20	$59.20	$59.20
Purchase #4	$170.82	8.517%	$185.3687	$185.37	$185.35	$185.40
Purchase #5	$176.91	7.662%	$190.4648	$190.46	$190.45	$190.50
Purchase #6	$188.67	10.699%	$208.8558	$208.86	$208.85	$208.90
Purchase #7	$18.82	3.419%	$19.4635	$19.46	$19.45	$19.50
7 purchase totals =	$858.02		$933.3418	$933.34	$933.30	$933.50