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	$187.25	5.113%	$196.8241	$196.82	$196.80	$196.80
Purchase #2	$137.75	5.382%	$145.1637	$145.16	$145.15	$145.20
Purchase #3	$62.30	7.361%	$66.8859	$66.89	$66.90	$66.90
Purchase #4	$24.95	12.395%	$28.0426	$28.04	$28.05	$28.00
Purchase #5	$80.62	11.749%	$90.092	$90.09	$90.10	$90.10
Purchase #6	$191.56	11.446%	$213.486	$213.49	$213.50	$213.50
Purchase #7	$159.39	11.628%	$177.9239	$177.92	$177.90	$177.90
7 purchase totals =	$843.82		$918.4182	$918.41	$918.40	$918.40