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	$162.69	9.307%	$177.8316	$177.83	$177.85	$177.80
Purchase #2	$108.65	11.487%	$121.1306	$121.13	$121.15	$121.10
Purchase #3	$236.72	10.616%	$261.8502	$261.85	$261.85	$261.90
Purchase #4	$115.93	6.854%	$123.8758	$123.88	$123.90	$123.90
Purchase #5	$237.54	13.189%	$268.8692	$268.87	$268.85	$268.90
Purchase #6	$81.53	11.512%	$90.9157	$90.92	$90.90	$90.90
Purchase #7	$48.92	3.471%	$50.618	$50.62	$50.60	$50.60
7 purchase totals =	$991.98		$1,095.0911	$1,095.10	$1,095.10	$1,095.10