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	$26.38	8.665%	$28.6658	$28.67	$28.65	$28.70
Purchase #2	$60.51	6.655%	$64.5369	$64.54	$64.55	$64.50
Purchase #3	$243.46	13.227%	$275.6625	$275.66	$275.65	$275.70
Purchase #4	$147.37	8.853%	$160.4167	$160.42	$160.40	$160.40
Purchase #5	$50.40	12.705%	$56.8033	$56.80	$56.80	$56.80
Purchase #6	$203.71	9.176%	$222.4024	$222.40	$222.40	$222.40
Purchase #7	$230.31	9.856%	$253.0094	$253.01	$253.00	$253.00
7 purchase totals =	$962.14		$1,061.4970	$1,061.50	$1,061.45	$1,061.50