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	$81.36	11.760%	$90.9279	$90.93	$90.95	$90.90
Purchase #2	$78.26	4.597%	$81.8576	$81.86	$81.85	$81.90
Purchase #3	$114.52	3.586%	$118.6267	$118.63	$118.65	$118.60
Purchase #4	$117.92	3.364%	$121.8868	$121.89	$121.90	$121.90
Purchase #5	$105.66	10.628%	$116.8895	$116.89	$116.90	$116.90
Purchase #6	$94.95	5.547%	$100.2169	$100.22	$100.20	$100.20
Purchase #7	$192.72	3.231%	$198.9468	$198.95	$198.95	$198.90
7 purchase totals =	$785.39		$829.3522	$829.37	$829.40	$829.30