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	$147.66	12.754%	$166.4926	$166.49	$166.50	$166.50
Purchase #2	$52.53	12.596%	$59.1467	$59.15	$59.15	$59.10
Purchase #3	$197.53	11.697%	$220.6351	$220.64	$220.65	$220.60
Purchase #4	$200.95	3.367%	$207.716	$207.72	$207.70	$207.70
Purchase #5	$56.54	5.508%	$59.6542	$59.65	$59.65	$59.70
Purchase #6	$149.72	9.871%	$164.4989	$164.50	$164.50	$164.50
Purchase #7	$198.30	10.230%	$218.5861	$218.59	$218.60	$218.60
7 purchase totals =	$1,003.23		$1,096.7296	$1,096.74	$1,096.75	$1,096.70