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	$207.42	12.225%	$232.7771	$232.78	$232.80	$232.80
Purchase #2	$47.46	10.825%	$52.5975	$52.60	$52.60	$52.60
Purchase #3	$228.32	4.457%	$238.4962	$238.50	$238.50	$238.50
Purchase #4	$43.73	3.809%	$45.3957	$45.40	$45.40	$45.40
Purchase #5	$36.31	12.551%	$40.8673	$40.87	$40.85	$40.90
Purchase #6	$133.45	7.604%	$143.5975	$143.60	$143.60	$143.60
Purchase #7	$132.25	11.629%	$147.6294	$147.63	$147.65	$147.60
7 purchase totals =	$828.94		$901.3607	$901.38	$901.40	$901.40