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	$114.60	3.794%	$118.9479	$118.95	$118.95	$118.90
Purchase #2	$23.90	13.373%	$27.0961	$27.10	$27.10	$27.10
Purchase #3	$210.46	10.336%	$232.2131	$232.21	$232.20	$232.20
Purchase #4	$167.62	7.126%	$179.5646	$179.56	$179.55	$179.60
Purchase #5	$99.73	12.154%	$111.8512	$111.85	$111.85	$111.90
Purchase #6	$68.83	12.622%	$77.5177	$77.52	$77.50	$77.50
Purchase #7	$148.84	10.434%	$164.37	$164.37	$164.35	$164.40
7 purchase totals =	$833.98		$911.5606	$911.56	$911.50	$911.60