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	$222.70	7.260%	$238.868	$238.87	$238.85	$238.90
Purchase #2	$178.33	9.159%	$194.6632	$194.66	$194.65	$194.70
Purchase #3	$117.90	4.410%	$123.0994	$123.10	$123.10	$123.10
Purchase #4	$120.94	5.743%	$127.8856	$127.89	$127.90	$127.90
Purchase #5	$29.25	9.833%	$32.1262	$32.13	$32.15	$32.10
Purchase #6	$21.59	7.513%	$23.2121	$23.21	$23.20	$23.20
Purchase #7	$54.88	6.228%	$58.2979	$58.30	$58.30	$58.30
7 purchase totals =	$745.59		$798.1524	$798.16	$798.15	$798.20