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	$42.59	12.384%	$47.8643	$47.86	$47.85	$47.90
Purchase #2	$127.44	10.580%	$140.9232	$140.92	$140.90	$140.90
Purchase #3	$219.55	6.638%	$234.1237	$234.12	$234.10	$234.10
Purchase #4	$54.80	8.642%	$59.5358	$59.54	$59.55	$59.50
Purchase #5	$213.78	11.205%	$237.734	$237.73	$237.75	$237.70
Purchase #6	$104.41	11.781%	$116.7105	$116.71	$116.70	$116.70
Purchase #7	$197.82	5.495%	$208.6902	$208.69	$208.70	$208.70
7 purchase totals =	$960.39		$1,045.5817	$1,045.57	$1,045.55	$1,045.50