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	$198.46	3.324%	$205.0568	$205.06	$205.05	$205.10
Purchase #2	$119.40	3.659%	$123.7688	$123.77	$123.75	$123.80
Purchase #3	$48.68	10.847%	$53.9603	$53.96	$53.95	$54.00
Purchase #4	$162.81	10.493%	$179.8937	$179.89	$179.90	$179.90
Purchase #5	$55.26	7.145%	$59.2083	$59.21	$59.20	$59.20
Purchase #6	$150.34	11.654%	$167.8606	$167.86	$167.85	$167.90
Purchase #7	$25.55	5.185%	$26.8748	$26.87	$26.85	$26.90
7 purchase totals =	$760.50		$816.6233	$816.62	$816.55	$816.80