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	$67.39	6.583%	$71.8263	$71.83	$71.85	$71.80
Purchase #2	$121.64	5.135%	$127.8862	$127.89	$127.90	$127.90
Purchase #3	$13.44	5.361%	$14.1605	$14.16	$14.15	$14.20
Purchase #4	$58.59	3.826%	$60.8317	$60.83	$60.85	$60.80
Purchase #5	$77.71	5.710%	$82.1472	$82.15	$82.15	$82.10
Purchase #6	$224.74	9.600%	$246.315	$246.32	$246.30	$246.30
Purchase #7	$208.68	12.675%	$235.1302	$235.13	$235.15	$235.10
7 purchase totals =	$772.19		$838.2971	$838.31	$838.35	$838.20