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	$156.46	10.343%	$172.6427	$172.64	$172.65	$172.60
Purchase #2	$156.71	13.352%	$177.6339	$177.63	$177.65	$177.60
Purchase #3	$24.45	4.517%	$25.5544	$25.55	$25.55	$25.60
Purchase #4	$31.64	5.847%	$33.49	$33.49	$33.50	$33.50
Purchase #5	$53.68	10.673%	$59.4093	$59.41	$59.40	$59.40
Purchase #6	$139.32	7.760%	$150.1312	$150.13	$150.15	$150.10
Purchase #7	$145.81	9.818%	$160.1256	$160.13	$160.15	$160.10
7 purchase totals =	$708.07		$778.9871	$778.98	$779.05	$778.90