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	$182.99	5.319%	$192.7232	$192.72	$192.70	$192.70
Purchase #2	$157.45	5.771%	$166.5364	$166.54	$166.55	$166.50
Purchase #3	$244.96	3.646%	$253.8912	$253.89	$253.90	$253.90
Purchase #4	$143.89	11.838%	$160.9237	$160.92	$160.90	$160.90
Purchase #5	$55.78	11.430%	$62.1557	$62.16	$62.15	$62.20
Purchase #6	$78.72	5.322%	$82.9095	$82.91	$82.90	$82.90
Purchase #7	$174.99	5.344%	$184.3415	$184.34	$184.35	$184.30
7 purchase totals =	$1,038.78		$1,103.4812	$1,103.48	$1,103.45	$1,103.40