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	$60.81	10.418%	$67.1452	$67.15	$67.15	$67.10
Purchase #2	$109.32	12.788%	$123.2998	$123.30	$123.30	$123.30
Purchase #3	$178.57	12.229%	$200.4073	$200.41	$200.40	$200.40
Purchase #4	$172.64	8.478%	$187.2764	$187.28	$187.30	$187.30
Purchase #5	$69.44	12.759%	$78.2998	$78.30	$78.30	$78.30
Purchase #6	$63.58	7.104%	$68.0967	$68.10	$68.10	$68.10
Purchase #7	$198.82	5.639%	$210.0315	$210.03	$210.05	$210.00
7 purchase totals =	$853.18		$934.5567	$934.57	$934.60	$934.50