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	$250.99	4.242%	$261.637	$261.64	$261.65	$261.60
Purchase #2	$75.53	13.680%	$85.8625	$85.86	$85.85	$85.90
Purchase #3	$207.79	9.690%	$227.9249	$227.92	$227.90	$227.90
Purchase #4	$83.47	4.262%	$87.0275	$87.03	$87.05	$87.00
Purchase #5	$87.26	3.293%	$90.1335	$90.13	$90.15	$90.10
Purchase #6	$175.90	13.709%	$200.0141	$200.01	$200.00	$200.00
Purchase #7	$172.39	4.575%	$180.2768	$180.28	$180.30	$180.30
7 purchase totals =	$1,053.33		$1,132.8763	$1,132.87	$1,132.90	$1,132.80