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	$141.76	7.462%	$152.3381	$152.34	$152.35	$152.30
Purchase #2	$54.81	11.646%	$61.1932	$61.19	$61.20	$61.20
Purchase #3	$131.39	3.814%	$136.4012	$136.40	$136.40	$136.40
Purchase #4	$68.29	5.188%	$71.8329	$71.83	$71.85	$71.80
Purchase #5	$237.85	12.440%	$267.4385	$267.44	$267.45	$267.40
Purchase #6	$36.78	11.127%	$40.8725	$40.87	$40.85	$40.90
Purchase #7	$18.80	3.764%	$19.5076	$19.51	$19.50	$19.50
7 purchase totals =	$689.68		$749.5840	$749.58	$749.60	$749.50