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	$76.37	8.405%	$82.7889	$82.79	$82.80	$82.80
Purchase #2	$38.58	8.298%	$41.7814	$41.78	$41.80	$41.80
Purchase #3	$82.80	8.874%	$90.1477	$90.15	$90.15	$90.10
Purchase #4	$159.38	10.163%	$175.5778	$175.58	$175.60	$175.60
Purchase #5	$50.55	13.420%	$57.3338	$57.33	$57.35	$57.30
Purchase #6	$154.63	4.511%	$161.6054	$161.61	$161.60	$161.60
Purchase #7	$198.66	7.397%	$213.3549	$213.35	$213.35	$213.40
7 purchase totals =	$760.97		$822.5899	$822.59	$822.65	$822.60