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	$45.36	4.501%	$47.4017	$47.40	$47.40	$47.40
Purchase #2	$10.84	5.770%	$11.4655	$11.47	$11.45	$11.50
Purchase #3	$26.79	10.216%	$29.5269	$29.53	$29.55	$29.50
Purchase #4	$215.79	6.240%	$229.2553	$229.26	$229.25	$229.30
Purchase #5	$202.72	12.238%	$227.5289	$227.53	$227.55	$227.50
Purchase #6	$214.49	3.727%	$222.484	$222.48	$222.50	$222.50
Purchase #7	$233.57	7.606%	$251.3353	$251.34	$251.35	$251.30
7 purchase totals =	$949.56		$1,018.9976	$1,019.01	$1,019.05	$1,019.00