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	$174.82	12.599%	$196.8456	$196.85	$196.85	$196.80
Purchase #2	$124.35	6.274%	$132.1517	$132.15	$132.15	$132.20
Purchase #3	$166.27	7.382%	$178.5441	$178.54	$178.55	$178.50
Purchase #4	$189.35	11.439%	$211.0097	$211.01	$211.00	$211.00
Purchase #5	$18.79	9.479%	$20.5711	$20.57	$20.55	$20.60
Purchase #6	$104.42	8.793%	$113.6017	$113.60	$113.60	$113.60
Purchase #7	$234.88	13.719%	$267.1032	$267.10	$267.10	$267.10
7 purchase totals =	$1,012.88		$1,119.8271	$1,119.82	$1,119.80	$1,119.80