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	$102.27	9.284%	$111.7647	$111.76	$111.75	$111.80
Purchase #2	$39.30	3.527%	$40.6861	$40.69	$40.70	$40.70
Purchase #3	$204.88	9.599%	$224.5464	$224.55	$224.55	$224.50
Purchase #4	$250.84	7.509%	$269.6756	$269.68	$269.70	$269.70
Purchase #5	$100.68	8.686%	$109.4251	$109.43	$109.45	$109.40
Purchase #6	$124.73	13.131%	$141.1083	$141.11	$141.10	$141.10
Purchase #7	$196.84	11.164%	$218.8152	$218.82	$218.80	$218.80
7 purchase totals =	$1,019.54		$1,116.0214	$1,116.04	$1,116.05	$1,116.00