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	$213.28	5.620%	$225.2663	$225.27	$225.25	$225.30
Purchase #2	$69.38	13.529%	$78.7664	$78.77	$78.75	$78.80
Purchase #3	$123.79	11.152%	$137.5951	$137.60	$137.60	$137.60
Purchase #4	$230.94	13.646%	$262.4541	$262.45	$262.45	$262.50
Purchase #5	$146.96	6.266%	$156.1685	$156.17	$156.15	$156.20
Purchase #6	$124.66	10.523%	$137.778	$137.78	$137.80	$137.80
Purchase #7	$189.47	10.365%	$209.1086	$209.11	$209.10	$209.10
7 purchase totals =	$1,098.48		$1,207.1370	$1,207.15	$1,207.10	$1,207.30