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	$15.98	5.526%	$16.8631	$16.86	$16.85	$16.90
Purchase #2	$30.29	4.232%	$31.5719	$31.57	$31.55	$31.60
Purchase #3	$141.27	7.532%	$151.9105	$151.91	$151.90	$151.90
Purchase #4	$168.49	9.754%	$184.9245	$184.92	$184.90	$184.90
Purchase #5	$171.78	12.194%	$192.7269	$192.73	$192.75	$192.70
Purchase #6	$158.42	7.253%	$169.9102	$169.91	$169.90	$169.90
Purchase #7	$17.43	5.467%	$18.3829	$18.38	$18.40	$18.40
7 purchase totals =	$703.66		$766.2900	$766.28	$766.25	$766.30