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	$196.37	7.666%	$211.4237	$211.42	$211.40	$211.40
Purchase #2	$151.85	12.364%	$170.6247	$170.62	$170.60	$170.60
Purchase #3	$123.47	3.631%	$127.9532	$127.95	$127.95	$128.00
Purchase #4	$214.63	3.596%	$222.3481	$222.35	$222.35	$222.30
Purchase #5	$120.48	8.612%	$130.8557	$130.86	$130.85	$130.90
Purchase #6	$156.35	12.841%	$176.4269	$176.43	$176.45	$176.40
Purchase #7	$167.79	9.449%	$183.6445	$183.64	$183.65	$183.60
7 purchase totals =	$1,130.94		$1,223.2768	$1,223.27	$1,223.25	$1,223.20