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	$15.67	7.570%	$16.8562	$16.86	$16.85	$16.90
Purchase #2	$170.51	11.411%	$189.9669	$189.97	$189.95	$190.00
Purchase #3	$40.60	4.615%	$42.4737	$42.47	$42.45	$42.50
Purchase #4	$43.90	7.631%	$47.25	$47.25	$47.25	$47.30
Purchase #5	$59.45	13.107%	$67.2421	$67.24	$67.25	$67.20
Purchase #6	$148.79	6.815%	$158.93	$158.93	$158.95	$158.90
Purchase #7	$228.82	6.696%	$244.1418	$244.14	$244.15	$244.10
7 purchase totals =	$707.74		$766.8607	$766.86	$766.85	$766.90