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	$206.85	11.379%	$230.3875	$230.39	$230.40	$230.40
Purchase #2	$71.31	13.705%	$81.083	$81.08	$81.10	$81.10
Purchase #3	$98.52	13.294%	$111.6172	$111.62	$111.60	$111.60
Purchase #4	$100.61	8.464%	$109.1256	$109.13	$109.15	$109.10
Purchase #5	$136.62	9.452%	$149.5333	$149.53	$149.55	$149.50
Purchase #6	$36.93	3.564%	$38.2462	$38.25	$38.25	$38.20
Purchase #7	$81.96	5.703%	$86.6342	$86.63	$86.65	$86.60
7 purchase totals =	$732.80		$806.6270	$806.63	$806.70	$806.50