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	$42.51	6.791%	$45.3969	$45.40	$45.40	$45.40
Purchase #2	$178.98	6.319%	$190.2897	$190.29	$190.30	$190.30
Purchase #3	$181.41	8.273%	$196.418	$196.42	$196.40	$196.40
Purchase #4	$174.80	5.854%	$185.0328	$185.03	$185.05	$185.00
Purchase #5	$41.85	11.116%	$46.502	$46.50	$46.50	$46.50
Purchase #6	$69.37	9.257%	$75.7916	$75.79	$75.80	$75.80
Purchase #7	$44.89	8.235%	$48.5867	$48.59	$48.60	$48.60
7 purchase totals =	$733.81		$788.0177	$788.02	$788.05	$788.00