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	$59.59	3.441%	$61.6405	$61.64	$61.65	$61.60
Purchase #2	$46.36	3.542%	$48.0021	$48.00	$48.00	$48.00
Purchase #3	$109.34	13.768%	$124.3939	$124.39	$124.40	$124.40
Purchase #4	$85.80	5.561%	$90.5713	$90.57	$90.55	$90.60
Purchase #5	$236.44	9.277%	$258.3745	$258.37	$258.35	$258.40
Purchase #6	$78.74	5.407%	$82.9975	$83.00	$83.00	$83.00
Purchase #7	$220.96	9.813%	$242.6428	$242.64	$242.65	$242.60
7 purchase totals =	$837.23		$908.6226	$908.61	$908.60	$908.60