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	$114.69	10.863%	$127.1488	$127.15	$127.15	$127.10
Purchase #2	$131.70	6.617%	$140.4146	$140.41	$140.40	$140.40
Purchase #3	$144.54	9.392%	$158.1152	$158.12	$158.10	$158.10
Purchase #4	$197.39	9.739%	$216.6138	$216.61	$216.60	$216.60
Purchase #5	$39.47	4.158%	$41.1112	$41.11	$41.10	$41.10
Purchase #6	$13.88	4.672%	$14.5285	$14.53	$14.55	$14.50
Purchase #7	$169.39	10.287%	$186.8151	$186.82	$186.80	$186.80
7 purchase totals =	$811.06		$884.7472	$884.75	$884.70	$884.60