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	$55.64	11.198%	$61.8706	$61.87	$61.85	$61.90
Purchase #2	$152.95	8.630%	$166.1496	$166.15	$166.15	$166.10
Purchase #3	$152.45	12.413%	$171.3736	$171.37	$171.35	$171.40
Purchase #4	$243.28	4.825%	$255.0183	$255.02	$255.00	$255.00
Purchase #5	$72.70	5.387%	$76.6163	$76.62	$76.60	$76.60
Purchase #6	$173.81	3.479%	$179.8568	$179.86	$179.85	$179.90
Purchase #7	$78.39	6.657%	$83.6084	$83.61	$83.60	$83.60
7 purchase totals =	$929.22		$994.4936	$994.50	$994.40	$994.50