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	$116.93	12.321%	$131.3369	$131.34	$131.35	$131.30
Purchase #2	$82.60	9.365%	$90.3355	$90.34	$90.35	$90.30
Purchase #3	$189.28	3.577%	$196.0505	$196.05	$196.05	$196.10
Purchase #4	$236.27	13.812%	$268.9036	$268.90	$268.90	$268.90
Purchase #5	$208.63	13.388%	$236.5614	$236.56	$236.55	$236.60
Purchase #6	$214.95	5.713%	$227.2301	$227.23	$227.25	$227.20
Purchase #7	$40.95	7.264%	$43.9246	$43.92	$43.90	$43.90
7 purchase totals =	$1,089.61		$1,194.3426	$1,194.34	$1,194.35	$1,194.30