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	$70.28	3.237%	$72.555	$72.56	$72.55	$72.60
Purchase #2	$90.39	11.762%	$101.0217	$101.02	$101.00	$101.00
Purchase #3	$169.98	10.336%	$187.5491	$187.55	$187.55	$187.50
Purchase #4	$166.50	8.198%	$180.1497	$180.15	$180.15	$180.10
Purchase #5	$213.62	5.705%	$225.807	$225.81	$225.80	$225.80
Purchase #6	$92.56	12.126%	$103.7838	$103.78	$103.80	$103.80
Purchase #7	$68.48	7.460%	$73.5886	$73.59	$73.60	$73.60
7 purchase totals =	$871.81		$944.4549	$944.46	$944.45	$944.40