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	$99.28	10.678%	$109.8811	$109.88	$109.90	$109.90
Purchase #2	$237.55	12.228%	$266.5976	$266.60	$266.60	$266.60
Purchase #3	$152.98	8.740%	$166.3505	$166.35	$166.35	$166.40
Purchase #4	$38.28	4.213%	$39.8927	$39.89	$39.90	$39.90
Purchase #5	$175.87	6.724%	$187.6955	$187.70	$187.70	$187.70
Purchase #6	$154.74	10.804%	$171.4581	$171.46	$171.45	$171.50
Purchase #7	$193.71	10.687%	$214.4118	$214.41	$214.40	$214.40
7 purchase totals =	$1,052.41		$1,156.2873	$1,156.29	$1,156.30	$1,156.40