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	$66.33	10.419%	$73.2409	$73.24	$73.25	$73.20
Purchase #2	$17.59	7.276%	$18.8698	$18.87	$18.85	$18.90
Purchase #3	$41.27	4.474%	$43.1164	$43.12	$43.10	$43.10
Purchase #4	$129.50	12.471%	$145.6499	$145.65	$145.65	$145.60
Purchase #5	$40.35	6.447%	$42.9514	$42.95	$42.95	$43.00
Purchase #6	$20.58	12.106%	$23.0714	$23.07	$23.05	$23.10
Purchase #7	$75.56	3.773%	$78.4109	$78.41	$78.40	$78.40
7 purchase totals =	$391.18		$425.3107	$425.31	$425.25	$425.30