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	$199.46	13.766%	$226.9177	$226.92	$226.90	$226.90
Purchase #2	$196.55	6.343%	$209.0172	$209.02	$209.00	$209.00
Purchase #3	$210.43	7.123%	$225.4189	$225.42	$225.40	$225.40
Purchase #4	$156.56	6.396%	$166.5736	$166.57	$166.55	$166.60
Purchase #5	$110.27	7.800%	$118.8711	$118.87	$118.85	$118.90
Purchase #6	$138.27	11.359%	$153.9761	$153.98	$154.00	$154.00
Purchase #7	$196.57	12.780%	$221.6916	$221.69	$221.70	$221.70
7 purchase totals =	$1,208.11		$1,322.4662	$1,322.47	$1,322.40	$1,322.50