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	$150.91	4.566%	$157.8006	$157.80	$157.80	$157.80
Purchase #2	$174.39	12.774%	$196.6666	$196.67	$196.65	$196.70
Purchase #3	$85.83	9.314%	$93.8242	$93.82	$93.80	$93.80
Purchase #4	$187.96	9.312%	$205.4628	$205.46	$205.45	$205.50
Purchase #5	$39.93	13.400%	$45.2806	$45.28	$45.30	$45.30
Purchase #6	$192.28	13.481%	$218.2013	$218.20	$218.20	$218.20
Purchase #7	$32.59	8.175%	$35.2542	$35.25	$35.25	$35.30
7 purchase totals =	$863.89		$952.4903	$952.48	$952.45	$952.60