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	$107.82	10.402%	$119.0354	$119.04	$119.05	$119.00
Purchase #2	$46.49	11.665%	$51.9131	$51.91	$51.90	$51.90
Purchase #3	$179.39	11.580%	$200.1634	$200.16	$200.15	$200.20
Purchase #4	$91.54	5.781%	$96.8319	$96.83	$96.85	$96.80
Purchase #5	$123.83	3.768%	$128.4959	$128.50	$128.50	$128.50
Purchase #6	$121.81	5.149%	$128.082	$128.08	$128.10	$128.10
Purchase #7	$80.41	10.185%	$88.5998	$88.60	$88.60	$88.60
7 purchase totals =	$751.29		$813.1215	$813.12	$813.15	$813.10