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	$66.57	7.620%	$71.6426	$71.64	$71.65	$71.60
Purchase #2	$201.99	11.255%	$224.724	$224.72	$224.70	$224.70
Purchase #3	$63.37	11.861%	$70.8863	$70.89	$70.90	$70.90
Purchase #4	$85.61	4.597%	$89.5455	$89.55	$89.55	$89.50
Purchase #5	$246.72	4.333%	$257.4104	$257.41	$257.40	$257.40
Purchase #6	$164.79	4.386%	$172.0177	$172.02	$172.00	$172.00
Purchase #7	$149.74	5.193%	$157.516	$157.52	$157.50	$157.50
7 purchase totals =	$978.79		$1,043.7425	$1,043.75	$1,043.70	$1,043.60