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	$23.85	11.166%	$26.5131	$26.51	$26.50	$26.50
Purchase #2	$223.94	4.283%	$233.5314	$233.53	$233.55	$233.50
Purchase #3	$95.81	6.343%	$101.8872	$101.89	$101.90	$101.90
Purchase #4	$224.50	6.257%	$238.547	$238.55	$238.55	$238.50
Purchase #5	$145.39	5.219%	$152.9779	$152.98	$153.00	$153.00
Purchase #6	$127.44	5.199%	$134.0656	$134.07	$134.05	$134.10
Purchase #7	$164.65	9.150%	$179.7155	$179.72	$179.70	$179.70
7 purchase totals =	$1,005.58		$1,067.2377	$1,067.25	$1,067.25	$1,067.20