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	$249.32	4.776%	$261.2275	$261.23	$261.25	$261.20
Purchase #2	$138.35	12.481%	$155.6175	$155.62	$155.60	$155.60
Purchase #3	$63.27	9.779%	$69.4572	$69.46	$69.45	$69.50
Purchase #4	$99.44	10.535%	$109.916	$109.92	$109.90	$109.90
Purchase #5	$131.65	4.265%	$137.2649	$137.26	$137.25	$137.30
Purchase #6	$40.37	4.387%	$42.141	$42.14	$42.15	$42.10
Purchase #7	$219.70	8.406%	$238.168	$238.17	$238.15	$238.20
7 purchase totals =	$942.10		$1,013.7921	$1,013.80	$1,013.75	$1,013.80