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	$96.48	9.653%	$105.7932	$105.79	$105.80	$105.80
Purchase #2	$235.59	10.870%	$261.1986	$261.20	$261.20	$261.20
Purchase #3	$88.57	7.334%	$95.0657	$95.07	$95.05	$95.10
Purchase #4	$109.81	12.499%	$123.5352	$123.54	$123.55	$123.50
Purchase #5	$196.28	8.393%	$212.7538	$212.75	$212.75	$212.80
Purchase #6	$239.81	5.735%	$253.5631	$253.56	$253.55	$253.60
Purchase #7	$19.90	7.789%	$21.45	$21.45	$21.45	$21.50
7 purchase totals =	$986.44		$1,073.3596	$1,073.36	$1,073.35	$1,073.50