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	$191.65	3.780%	$198.8944	$198.89	$198.90	$198.90
Purchase #2	$16.34	9.366%	$17.8704	$17.87	$17.85	$17.90
Purchase #3	$123.87	3.229%	$127.8698	$127.87	$127.85	$127.90
Purchase #4	$227.74	10.573%	$251.819	$251.82	$251.80	$251.80
Purchase #5	$56.55	5.137%	$59.455	$59.46	$59.45	$59.50
Purchase #6	$147.43	5.539%	$155.5961	$155.60	$155.60	$155.60
Purchase #7	$210.90	3.135%	$217.5117	$217.51	$217.50	$217.50
7 purchase totals =	$974.48		$1,029.0164	$1,029.02	$1,028.95	$1,029.10