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	$66.84	8.120%	$72.2674	$72.27	$72.25	$72.30
Purchase #2	$135.77	5.224%	$142.8626	$142.86	$142.85	$142.90
Purchase #3	$245.81	4.477%	$256.8149	$256.81	$256.80	$256.80
Purchase #4	$197.47	3.212%	$203.8127	$203.81	$203.80	$203.80
Purchase #5	$171.47	4.175%	$178.6289	$178.63	$178.65	$178.60
Purchase #6	$52.88	6.197%	$56.157	$56.16	$56.15	$56.20
Purchase #7	$82.47	10.766%	$91.3487	$91.35	$91.35	$91.30
7 purchase totals =	$952.71		$1,001.8922	$1,001.89	$1,001.85	$1,001.90