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	$184.98	8.450%	$200.6108	$200.61	$200.60	$200.60
Purchase #2	$48.94	3.460%	$50.6333	$50.63	$50.65	$50.60
Purchase #3	$36.91	4.705%	$38.6466	$38.65	$38.65	$38.60
Purchase #4	$48.28	11.154%	$53.6652	$53.67	$53.65	$53.70
Purchase #5	$19.84	10.419%	$21.9071	$21.91	$21.90	$21.90
Purchase #6	$219.86	10.333%	$242.5781	$242.58	$242.60	$242.60
Purchase #7	$122.61	12.103%	$137.4495	$137.45	$137.45	$137.40
7 purchase totals =	$681.42		$745.4906	$745.50	$745.50	$745.40