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	$147.52	7.470%	$158.5397	$158.54	$158.55	$158.50
Purchase #2	$54.98	13.622%	$62.4694	$62.47	$62.45	$62.50
Purchase #3	$49.52	5.755%	$52.3699	$52.37	$52.35	$52.40
Purchase #4	$103.84	7.770%	$111.9084	$111.91	$111.90	$111.90
Purchase #5	$246.34	4.266%	$256.8489	$256.85	$256.85	$256.80
Purchase #6	$144.50	8.613%	$156.9458	$156.95	$156.95	$156.90
Purchase #7	$169.89	9.107%	$185.3619	$185.36	$185.35	$185.40
7 purchase totals =	$916.59		$984.4440	$984.45	$984.40	$984.40