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	$120.71	6.116%	$128.0926	$128.09	$128.10	$128.10
Purchase #2	$67.99	6.677%	$72.5297	$72.53	$72.55	$72.50
Purchase #3	$142.69	10.806%	$158.1091	$158.11	$158.10	$158.10
Purchase #4	$196.46	9.310%	$214.7504	$214.75	$214.75	$214.80
Purchase #5	$205.85	3.382%	$212.8118	$212.81	$212.80	$212.80
Purchase #6	$204.83	3.670%	$212.3473	$212.35	$212.35	$212.30
Purchase #7	$134.25	7.459%	$144.2637	$144.26	$144.25	$144.30
7 purchase totals =	$1,072.78		$1,142.9046	$1,142.90	$1,142.90	$1,142.90