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	$236.39	4.455%	$246.9212	$246.92	$246.90	$246.90
Purchase #2	$80.92	10.860%	$89.7079	$89.71	$89.70	$89.70
Purchase #3	$40.90	11.108%	$45.4432	$45.44	$45.45	$45.40
Purchase #4	$119.44	9.600%	$130.9062	$130.91	$130.90	$130.90
Purchase #5	$154.42	12.208%	$173.2716	$173.27	$173.25	$173.30
Purchase #6	$249.67	13.411%	$283.1532	$283.15	$283.15	$283.20
Purchase #7	$78.39	10.394%	$86.5379	$86.54	$86.55	$86.50
7 purchase totals =	$960.13		$1,055.9412	$1,055.94	$1,055.90	$1,055.90