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	$188.33	13.534%	$213.8186	$213.82	$213.80	$213.80
Purchase #2	$137.72	7.712%	$148.341	$148.34	$148.35	$148.30
Purchase #3	$50.72	3.314%	$52.4009	$52.40	$52.40	$52.40
Purchase #4	$187.92	4.283%	$195.9686	$195.97	$195.95	$196.00
Purchase #5	$158.71	5.748%	$167.8327	$167.83	$167.85	$167.80
Purchase #6	$30.50	5.536%	$32.1885	$32.19	$32.20	$32.20
Purchase #7	$230.43	11.489%	$256.9041	$256.90	$256.90	$256.90
7 purchase totals =	$984.33		$1,067.4544	$1,067.45	$1,067.45	$1,067.40