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	$204.88	8.783%	$222.8746	$222.87	$222.85	$222.90
Purchase #2	$74.27	9.242%	$81.134	$81.13	$81.15	$81.10
Purchase #3	$237.30	7.574%	$255.2731	$255.27	$255.25	$255.30
Purchase #4	$61.82	11.641%	$69.0165	$69.02	$69.00	$69.00
Purchase #5	$57.37	4.336%	$59.8576	$59.86	$59.85	$59.90
Purchase #6	$125.63	5.398%	$132.4115	$132.41	$132.40	$132.40
Purchase #7	$100.69	9.330%	$110.0844	$110.08	$110.10	$110.10
7 purchase totals =	$861.96		$930.6517	$930.64	$930.60	$930.70