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	$134.99	11.333%	$150.2884	$150.29	$150.30	$150.30
Purchase #2	$237.60	7.757%	$256.0306	$256.03	$256.05	$256.00
Purchase #3	$117.73	7.520%	$126.5833	$126.58	$126.60	$126.60
Purchase #4	$236.57	9.590%	$259.2571	$259.26	$259.25	$259.30
Purchase #5	$77.78	5.482%	$82.0439	$82.04	$82.05	$82.00
Purchase #6	$111.76	10.413%	$123.3976	$123.40	$123.40	$123.40
Purchase #7	$57.98	5.429%	$61.1277	$61.13	$61.15	$61.10
7 purchase totals =	$974.41		$1,058.7286	$1,058.73	$1,058.80	$1,058.70