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	$143.35	8.814%	$155.9849	$155.98	$156.00	$156.00
Purchase #2	$118.79	7.609%	$127.8287	$127.83	$127.85	$127.80
Purchase #3	$182.74	3.628%	$189.3698	$189.37	$189.35	$189.40
Purchase #4	$83.83	4.231%	$87.3768	$87.38	$87.40	$87.40
Purchase #5	$203.60	4.748%	$213.2669	$213.27	$213.25	$213.30
Purchase #6	$126.98	3.332%	$131.211	$131.21	$131.20	$131.20
Purchase #7	$153.59	9.268%	$167.8247	$167.82	$167.80	$167.80
7 purchase totals =	$1,012.88		$1,072.8628	$1,072.86	$1,072.85	$1,072.90