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	$43.37	7.504%	$46.6245	$46.62	$46.60	$46.60
Purchase #2	$116.90	11.699%	$130.5761	$130.58	$130.60	$130.60
Purchase #3	$139.32	12.389%	$156.5804	$156.58	$156.60	$156.60
Purchase #4	$165.97	5.368%	$174.8793	$174.88	$174.90	$174.90
Purchase #5	$30.38	3.355%	$31.3992	$31.40	$31.40	$31.40
Purchase #6	$182.42	8.781%	$198.4383	$198.44	$198.45	$198.40
Purchase #7	$151.40	12.866%	$170.8791	$170.88	$170.90	$170.90
7 purchase totals =	$829.76		$909.3769	$909.38	$909.45	$909.40