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	$45.40	5.829%	$48.0464	$48.05	$48.05	$48.00
Purchase #2	$234.66	5.165%	$246.7802	$246.78	$246.80	$246.80
Purchase #3	$224.40	6.289%	$238.5125	$238.51	$238.50	$238.50
Purchase #4	$167.50	9.449%	$183.3271	$183.33	$183.35	$183.30
Purchase #5	$210.41	8.571%	$228.4442	$228.44	$228.45	$228.40
Purchase #6	$41.72	9.665%	$45.7522	$45.75	$45.75	$45.80
Purchase #7	$97.83	13.559%	$111.0948	$111.09	$111.10	$111.10
7 purchase totals =	$1,021.92		$1,101.9574	$1,101.95	$1,102.00	$1,101.90