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	$34.83	7.350%	$37.39	$37.39	$37.40	$37.40
Purchase #2	$236.42	3.176%	$243.9287	$243.93	$243.95	$243.90
Purchase #3	$105.96	8.639%	$115.1139	$115.11	$115.10	$115.10
Purchase #4	$141.55	8.189%	$153.1415	$153.14	$153.15	$153.10
Purchase #5	$145.81	7.408%	$156.6116	$156.61	$156.60	$156.60
Purchase #6	$197.55	11.197%	$219.6697	$219.67	$219.65	$219.70
Purchase #7	$173.99	6.687%	$185.6247	$185.62	$185.60	$185.60
7 purchase totals =	$1,036.11		$1,111.4801	$1,111.47	$1,111.45	$1,111.40