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	$102.43	9.870%	$112.5398	$112.54	$112.55	$112.50
Purchase #2	$102.83	13.535%	$116.748	$116.75	$116.75	$116.70
Purchase #3	$13.75	4.295%	$14.3406	$14.34	$14.35	$14.30
Purchase #4	$249.53	3.680%	$258.7127	$258.71	$258.70	$258.70
Purchase #5	$172.78	3.120%	$178.1707	$178.17	$178.15	$178.20
Purchase #6	$82.27	4.320%	$85.8241	$85.82	$85.80	$85.80
Purchase #7	$156.29	9.596%	$171.2876	$171.29	$171.30	$171.30
7 purchase totals =	$879.88		$937.6235	$937.62	$937.60	$937.50