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	$238.57	6.284%	$253.5617	$253.56	$253.55	$253.60
Purchase #2	$19.60	13.676%	$22.2805	$22.28	$22.30	$22.30
Purchase #3	$124.93	13.265%	$141.502	$141.50	$141.50	$141.50
Purchase #4	$66.33	10.134%	$73.0519	$73.05	$73.05	$73.10
Purchase #5	$73.38	12.624%	$82.6435	$82.64	$82.65	$82.60
Purchase #6	$147.52	13.799%	$167.8763	$167.88	$167.90	$167.90
Purchase #7	$118.58	11.864%	$132.6483	$132.65	$132.65	$132.60
7 purchase totals =	$788.91		$873.5642	$873.56	$873.60	$873.60