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	$213.61	11.489%	$238.1517	$238.15	$238.15	$238.20
Purchase #2	$93.85	7.686%	$101.0633	$101.06	$101.05	$101.10
Purchase #3	$234.49	11.102%	$260.5231	$260.52	$260.50	$260.50
Purchase #4	$214.52	11.257%	$238.6685	$238.67	$238.65	$238.70
Purchase #5	$228.55	13.827%	$260.1516	$260.15	$260.15	$260.20
Purchase #6	$159.46	3.516%	$165.0666	$165.07	$165.05	$165.10
Purchase #7	$78.70	4.679%	$82.3824	$82.38	$82.40	$82.40
7 purchase totals =	$1,223.18		$1,346.0072	$1,346.00	$1,345.95	$1,346.20