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	$181.45	10.366%	$200.2591	$200.26	$200.25	$200.30
Purchase #2	$132.85	7.573%	$142.9107	$142.91	$142.90	$142.90
Purchase #3	$139.76	8.259%	$151.3028	$151.30	$151.30	$151.30
Purchase #4	$106.86	12.174%	$119.8691	$119.87	$119.85	$119.90
Purchase #5	$100.92	10.357%	$111.3723	$111.37	$111.35	$111.40
Purchase #6	$9.59	8.412%	$10.3967	$10.40	$10.40	$10.40
Purchase #7	$215.94	11.818%	$241.4598	$241.46	$241.45	$241.50
7 purchase totals =	$887.37		$977.5705	$977.57	$977.50	$977.70