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	$199.74	5.527%	$210.7796	$210.78	$210.80	$210.80
Purchase #2	$160.38	9.497%	$175.6113	$175.61	$175.60	$175.60
Purchase #3	$90.98	6.537%	$96.9274	$96.93	$96.95	$96.90
Purchase #4	$35.94	12.644%	$40.4843	$40.48	$40.50	$40.50
Purchase #5	$78.61	5.505%	$82.9375	$82.94	$82.95	$82.90
Purchase #6	$235.71	7.134%	$252.5256	$252.53	$252.55	$252.50
Purchase #7	$231.60	11.730%	$258.7667	$258.77	$258.75	$258.80
7 purchase totals =	$1,032.96		$1,118.0324	$1,118.04	$1,118.10	$1,118.00