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	$152.41	4.721%	$159.6053	$159.61	$159.60	$159.60
Purchase #2	$72.37	8.478%	$78.5055	$78.51	$78.50	$78.50
Purchase #3	$18.47	7.624%	$19.8782	$19.88	$19.90	$19.90
Purchase #4	$40.51	4.827%	$42.4654	$42.47	$42.45	$42.50
Purchase #5	$138.93	12.751%	$156.645	$156.65	$156.65	$156.60
Purchase #6	$98.61	7.308%	$105.8164	$105.82	$105.80	$105.80
Purchase #7	$171.59	6.470%	$182.6919	$182.69	$182.70	$182.70
7 purchase totals =	$692.89		$745.6077	$745.63	$745.60	$745.60