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	$152.35	13.510%	$172.9325	$172.93	$172.95	$172.90
Purchase #2	$156.72	6.840%	$167.4396	$167.44	$167.45	$167.40
Purchase #3	$136.86	4.587%	$143.1378	$143.14	$143.15	$143.10
Purchase #4	$243.80	8.221%	$263.8428	$263.84	$263.85	$263.80
Purchase #5	$52.29	3.792%	$54.2728	$54.27	$54.25	$54.30
Purchase #6	$94.95	8.329%	$102.8584	$102.86	$102.85	$102.90
Purchase #7	$92.62	9.303%	$101.2364	$101.24	$101.25	$101.20
7 purchase totals =	$929.59		$1,005.7203	$1,005.72	$1,005.75	$1,005.60