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	$204.71	3.784%	$212.4562	$212.46	$212.45	$212.50
Purchase #2	$84.91	5.816%	$89.8484	$89.85	$89.85	$89.80
Purchase #3	$193.86	3.471%	$200.5889	$200.59	$200.60	$200.60
Purchase #4	$215.96	11.413%	$240.6075	$240.61	$240.60	$240.60
Purchase #5	$132.91	6.128%	$141.0547	$141.05	$141.05	$141.10
Purchase #6	$157.41	9.241%	$171.9563	$171.96	$171.95	$172.00
Purchase #7	$187.70	8.389%	$203.4462	$203.45	$203.45	$203.40
7 purchase totals =	$1,177.46		$1,259.9582	$1,259.97	$1,259.95	$1,260.00