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	$36.29	3.406%	$37.526	$37.53	$37.55	$37.50
Purchase #2	$105.66	11.191%	$117.4844	$117.48	$117.50	$117.50
Purchase #3	$113.98	11.571%	$127.1686	$127.17	$127.15	$127.20
Purchase #4	$126.32	12.584%	$142.2161	$142.22	$142.20	$142.20
Purchase #5	$104.41	13.747%	$118.7632	$118.76	$118.75	$118.80
Purchase #6	$181.37	7.599%	$195.1523	$195.15	$195.15	$195.20
Purchase #7	$21.35	9.522%	$23.3829	$23.38	$23.40	$23.40
7 purchase totals =	$689.38		$761.6935	$761.69	$761.70	$761.80