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	$49.34	4.415%	$51.5184	$51.52	$51.50	$51.50
Purchase #2	$132.64	7.106%	$142.0654	$142.07	$142.05	$142.10
Purchase #3	$139.47	9.622%	$152.8898	$152.89	$152.90	$152.90
Purchase #4	$6.33	9.383%	$6.9239	$6.92	$6.90	$6.90
Purchase #5	$113.40	10.571%	$125.3875	$125.39	$125.40	$125.40
Purchase #6	$244.50	9.849%	$268.5808	$268.58	$268.60	$268.60
Purchase #7	$35.69	10.222%	$39.3382	$39.34	$39.35	$39.30
7 purchase totals =	$721.37		$786.7040	$786.71	$786.70	$786.70