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	$190.44	13.812%	$216.7436	$216.74	$216.75	$216.70
Purchase #2	$15.61	6.799%	$16.6713	$16.67	$16.65	$16.70
Purchase #3	$12.31	6.271%	$13.082	$13.08	$13.10	$13.10
Purchase #4	$134.43	7.831%	$144.9572	$144.96	$144.95	$145.00
Purchase #5	$86.29	3.596%	$89.393	$89.39	$89.40	$89.40
Purchase #6	$105.98	3.332%	$109.5113	$109.51	$109.50	$109.50
Purchase #7	$160.59	3.747%	$166.6073	$166.61	$166.60	$166.60
7 purchase totals =	$705.65		$756.9657	$756.96	$756.95	$757.00