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	$43.53	3.871%	$45.215	$45.22	$45.20	$45.20
Purchase #2	$120.80	10.321%	$133.2678	$133.27	$133.25	$133.30
Purchase #3	$17.56	6.133%	$18.637	$18.64	$18.65	$18.60
Purchase #4	$82.86	5.402%	$87.3361	$87.34	$87.35	$87.30
Purchase #5	$18.51	9.235%	$20.2194	$20.22	$20.20	$20.20
Purchase #6	$200.31	10.543%	$221.4287	$221.43	$221.45	$221.40
Purchase #7	$95.39	4.853%	$100.0193	$100.02	$100.00	$100.00
7 purchase totals =	$578.96		$626.1233	$626.14	$626.10	$626.00