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	$84.46	7.281%	$90.6095	$90.61	$90.60	$90.60
Purchase #2	$188.76	3.334%	$195.0533	$195.05	$195.05	$195.10
Purchase #3	$171.44	13.720%	$194.9616	$194.96	$194.95	$195.00
Purchase #4	$111.80	10.280%	$123.293	$123.29	$123.30	$123.30
Purchase #5	$83.38	8.409%	$90.3914	$90.39	$90.40	$90.40
Purchase #6	$150.83	12.408%	$169.545	$169.55	$169.55	$169.50
Purchase #7	$11.92	6.648%	$12.7124	$12.71	$12.70	$12.70
7 purchase totals =	$802.59		$876.5662	$876.56	$876.55	$876.60