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	$229.56	6.742%	$245.0369	$245.04	$245.05	$245.00
Purchase #2	$164.92	13.626%	$187.392	$187.39	$187.40	$187.40
Purchase #3	$19.81	9.733%	$21.7381	$21.74	$21.75	$21.70
Purchase #4	$55.86	8.384%	$60.5433	$60.54	$60.55	$60.50
Purchase #5	$36.81	8.849%	$40.0673	$40.07	$40.05	$40.10
Purchase #6	$119.43	10.427%	$131.883	$131.88	$131.90	$131.90
Purchase #7	$167.84	3.460%	$173.6473	$173.65	$173.65	$173.60
7 purchase totals =	$794.23		$860.3079	$860.31	$860.35	$860.20