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	$137.66	6.383%	$146.4468	$146.45	$146.45	$146.40
Purchase #2	$126.86	3.499%	$131.2988	$131.30	$131.30	$131.30
Purchase #3	$213.72	10.725%	$236.6415	$236.64	$236.65	$236.60
Purchase #4	$76.27	13.537%	$86.5947	$86.59	$86.60	$86.60
Purchase #5	$237.81	12.850%	$268.3686	$268.37	$268.35	$268.40
Purchase #6	$119.28	6.382%	$126.8924	$126.89	$126.90	$126.90
Purchase #7	$105.26	3.344%	$108.7799	$108.78	$108.80	$108.80
7 purchase totals =	$1,016.86		$1,105.0227	$1,105.02	$1,105.05	$1,105.00