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	$61.36	10.606%	$67.8678	$67.87	$67.85	$67.90
Purchase #2	$117.41	12.146%	$131.6706	$131.67	$131.65	$131.70
Purchase #3	$204.92	12.751%	$231.0493	$231.05	$231.05	$231.00
Purchase #4	$52.73	12.164%	$59.1441	$59.14	$59.15	$59.10
Purchase #5	$178.84	8.734%	$194.4599	$194.46	$194.45	$194.50
Purchase #6	$110.27	10.273%	$121.598	$121.60	$121.60	$121.60
Purchase #7	$38.80	11.752%	$43.3598	$43.36	$43.35	$43.40
7 purchase totals =	$764.33		$849.1495	$849.15	$849.10	$849.20