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	$160.96	8.186%	$174.1362	$174.14	$174.15	$174.10
Purchase #2	$62.89	7.848%	$67.8256	$67.83	$67.85	$67.80
Purchase #3	$133.44	9.600%	$146.2502	$146.25	$146.25	$146.30
Purchase #4	$118.27	8.105%	$127.8558	$127.86	$127.85	$127.90
Purchase #5	$211.32	12.862%	$238.5	$238.50	$238.50	$238.50
Purchase #6	$26.91	9.828%	$29.5547	$29.55	$29.55	$29.60
Purchase #7	$221.98	11.225%	$246.8973	$246.90	$246.90	$246.90
7 purchase totals =	$935.77		$1,031.0198	$1,031.03	$1,031.05	$1,031.10