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	$114.38	3.673%	$118.5812	$118.58	$118.60	$118.60
Purchase #2	$148.31	4.733%	$155.3295	$155.33	$155.35	$155.30
Purchase #3	$119.88	5.115%	$126.0119	$126.01	$126.00	$126.00
Purchase #4	$51.38	7.727%	$55.3501	$55.35	$55.35	$55.40
Purchase #5	$82.86	7.439%	$89.024	$89.02	$89.00	$89.00
Purchase #6	$184.44	11.861%	$206.3164	$206.32	$206.30	$206.30
Purchase #7	$151.75	7.308%	$162.8399	$162.84	$162.85	$162.80
7 purchase totals =	$853.00		$913.4530	$913.45	$913.45	$913.40