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	$78.33	5.667%	$82.769	$82.77	$82.75	$82.80
Purchase #2	$150.93	13.807%	$171.7689	$171.77	$171.75	$171.80
Purchase #3	$188.98	13.460%	$214.4167	$214.42	$214.40	$214.40
Purchase #4	$24.60	13.181%	$27.8425	$27.84	$27.85	$27.80
Purchase #5	$133.75	13.610%	$151.9534	$151.95	$151.95	$152.00
Purchase #6	$194.51	5.602%	$205.4065	$205.41	$205.40	$205.40
Purchase #7	$233.51	3.424%	$241.5054	$241.51	$241.50	$241.50
7 purchase totals =	$1,004.61		$1,095.6624	$1,095.67	$1,095.60	$1,095.70