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	$98.86	12.513%	$111.2304	$111.23	$111.25	$111.20
Purchase #2	$64.52	4.661%	$67.5273	$67.53	$67.55	$67.50
Purchase #3	$178.95	10.864%	$198.3911	$198.39	$198.40	$198.40
Purchase #4	$109.60	5.472%	$115.5973	$115.60	$115.60	$115.60
Purchase #5	$155.32	8.850%	$169.0658	$169.07	$169.05	$169.10
Purchase #6	$204.27	7.140%	$218.8549	$218.85	$218.85	$218.90
Purchase #7	$9.31	6.693%	$9.9331	$9.93	$9.95	$9.90
7 purchase totals =	$820.83		$890.5999	$890.60	$890.65	$890.60