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	$225.51	3.752%	$233.9711	$233.97	$233.95	$234.00
Purchase #2	$171.40	9.314%	$187.3642	$187.36	$187.35	$187.40
Purchase #3	$63.46	6.377%	$67.5068	$67.51	$67.50	$67.50
Purchase #4	$200.69	4.358%	$209.4361	$209.44	$209.45	$209.40
Purchase #5	$130.37	13.730%	$148.2698	$148.27	$148.25	$148.30
Purchase #6	$144.32	8.147%	$156.0778	$156.08	$156.10	$156.10
Purchase #7	$50.81	3.511%	$52.5939	$52.59	$52.60	$52.60
7 purchase totals =	$986.56		$1,055.2197	$1,055.22	$1,055.20	$1,055.30