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	$116.71	8.831%	$127.0167	$127.02	$127.00	$127.00
Purchase #2	$48.31	11.260%	$53.7497	$53.75	$53.75	$53.70
Purchase #3	$27.78	13.592%	$31.5559	$31.56	$31.55	$31.60
Purchase #4	$153.53	12.227%	$172.3021	$172.30	$172.30	$172.30
Purchase #5	$67.35	8.293%	$72.9353	$72.94	$72.95	$72.90
Purchase #6	$82.83	10.295%	$91.3573	$91.36	$91.35	$91.40
Purchase #7	$29.85	5.171%	$31.3935	$31.39	$31.40	$31.40
7 purchase totals =	$526.36		$580.3105	$580.32	$580.30	$580.30