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	$183.72	4.223%	$191.4785	$191.48	$191.50	$191.50
Purchase #2	$206.93	12.303%	$232.3886	$232.39	$232.40	$232.40
Purchase #3	$152.54	8.698%	$165.8079	$165.81	$165.80	$165.80
Purchase #4	$56.84	5.379%	$59.8974	$59.90	$59.90	$59.90
Purchase #5	$151.47	10.259%	$167.0093	$167.01	$167.00	$167.00
Purchase #6	$230.95	3.418%	$238.8439	$238.84	$238.85	$238.80
Purchase #7	$109.26	9.327%	$119.4507	$119.45	$119.45	$119.50
7 purchase totals =	$1,091.71		$1,174.8763	$1,174.88	$1,174.90	$1,174.90