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	$167.43	13.858%	$190.6324	$190.63	$190.65	$190.60
Purchase #2	$44.29	11.715%	$49.4786	$49.48	$49.50	$49.50
Purchase #3	$66.70	7.817%	$71.9139	$71.91	$71.90	$71.90
Purchase #4	$53.33	4.565%	$55.7645	$55.76	$55.75	$55.80
Purchase #5	$53.70	11.421%	$59.8331	$59.83	$59.85	$59.80
Purchase #6	$35.31	3.700%	$36.6165	$36.62	$36.60	$36.60
Purchase #7	$132.68	6.602%	$141.4395	$141.44	$141.45	$141.40
7 purchase totals =	$553.44		$605.6785	$605.67	$605.70	$605.60