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	$107.96	4.637%	$112.9661	$112.97	$112.95	$113.00
Purchase #2	$91.89	12.768%	$103.6225	$103.62	$103.60	$103.60
Purchase #3	$198.96	10.273%	$219.3992	$219.40	$219.40	$219.40
Purchase #4	$235.79	13.189%	$266.8883	$266.89	$266.90	$266.90
Purchase #5	$143.90	3.228%	$148.5451	$148.55	$148.55	$148.50
Purchase #6	$109.89	8.380%	$119.0988	$119.10	$119.10	$119.10
Purchase #7	$86.66	11.112%	$96.2897	$96.29	$96.30	$96.30
7 purchase totals =	$975.05		$1,066.8097	$1,066.82	$1,066.80	$1,066.80