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	$198.94	12.486%	$223.7796	$223.78	$223.80	$223.80
Purchase #2	$107.29	10.214%	$118.2486	$118.25	$118.25	$118.20
Purchase #3	$130.30	12.131%	$146.1067	$146.11	$146.10	$146.10
Purchase #4	$40.93	7.278%	$43.9089	$43.91	$43.90	$43.90
Purchase #5	$211.69	5.425%	$223.1742	$223.17	$223.15	$223.20
Purchase #6	$150.37	5.299%	$158.3381	$158.34	$158.35	$158.30
Purchase #7	$166.60	4.780%	$174.5635	$174.56	$174.55	$174.60
7 purchase totals =	$1,006.12		$1,088.1196	$1,088.12	$1,088.10	$1,088.10