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	$35.63	4.812%	$37.3445	$37.34	$37.35	$37.30
Purchase #2	$228.38	11.871%	$255.491	$255.49	$255.50	$255.50
Purchase #3	$44.75	7.860%	$48.2674	$48.27	$48.25	$48.30
Purchase #4	$223.27	5.447%	$235.4315	$235.43	$235.45	$235.40
Purchase #5	$88.69	6.371%	$94.3404	$94.34	$94.35	$94.30
Purchase #6	$117.80	7.712%	$126.8847	$126.88	$126.90	$126.90
Purchase #7	$116.25	6.275%	$123.5447	$123.54	$123.55	$123.50
7 purchase totals =	$854.77		$921.3042	$921.29	$921.35	$921.20