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	$120.85	8.423%	$131.0292	$131.03	$131.05	$131.00
Purchase #2	$92.31	12.118%	$103.4961	$103.50	$103.50	$103.50
Purchase #3	$94.70	11.462%	$105.5545	$105.55	$105.55	$105.60
Purchase #4	$129.28	12.138%	$144.972	$144.97	$144.95	$145.00
Purchase #5	$191.75	11.784%	$214.3458	$214.35	$214.35	$214.30
Purchase #6	$186.86	3.847%	$194.0485	$194.05	$194.05	$194.00
Purchase #7	$59.78	12.628%	$67.329	$67.33	$67.35	$67.30
7 purchase totals =	$875.53		$960.7751	$960.78	$960.80	$960.70