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	$246.57	7.321%	$264.6214	$264.62	$264.60	$264.60
Purchase #2	$143.58	11.191%	$159.648	$159.65	$159.65	$159.60
Purchase #3	$13.53	3.567%	$14.0126	$14.01	$14.00	$14.00
Purchase #4	$102.82	7.190%	$110.2128	$110.21	$110.20	$110.20
Purchase #5	$193.55	11.356%	$215.5295	$215.53	$215.55	$215.50
Purchase #6	$244.72	7.366%	$262.7461	$262.75	$262.75	$262.70
Purchase #7	$178.76	10.127%	$196.863	$196.86	$196.85	$196.90
7 purchase totals =	$1,123.53		$1,223.6334	$1,223.63	$1,223.60	$1,223.50