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	$223.63	6.211%	$237.5197	$237.52	$237.50	$237.50
Purchase #2	$10.66	8.447%	$11.5605	$11.56	$11.55	$11.60
Purchase #3	$207.56	12.756%	$234.0364	$234.04	$234.05	$234.00
Purchase #4	$116.58	9.260%	$127.3753	$127.38	$127.40	$127.40
Purchase #5	$219.30	8.696%	$238.3703	$238.37	$238.35	$238.40
Purchase #6	$203.96	9.295%	$222.9181	$222.92	$222.90	$222.90
Purchase #7	$46.79	13.238%	$52.9841	$52.98	$53.00	$53.00
7 purchase totals =	$1,028.48		$1,124.7644	$1,124.77	$1,124.75	$1,124.80