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	$72.53	4.442%	$75.7518	$75.75	$75.75	$75.80
Purchase #2	$31.35	11.189%	$34.8578	$34.86	$34.85	$34.90
Purchase #3	$231.64	11.654%	$258.6353	$258.64	$258.65	$258.60
Purchase #4	$134.51	7.736%	$144.9157	$144.92	$144.90	$144.90
Purchase #5	$218.96	5.209%	$230.3656	$230.37	$230.35	$230.40
Purchase #6	$82.86	9.114%	$90.4119	$90.41	$90.40	$90.40
Purchase #7	$209.89	10.822%	$232.6043	$232.60	$232.60	$232.60
7 purchase totals =	$981.74		$1,067.5424	$1,067.55	$1,067.50	$1,067.60