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	$224.44	11.180%	$249.5324	$249.53	$249.55	$249.50
Purchase #2	$131.97	10.338%	$145.6131	$145.61	$145.60	$145.60
Purchase #3	$240.89	5.221%	$253.4669	$253.47	$253.45	$253.50
Purchase #4	$176.64	11.310%	$196.618	$196.62	$196.60	$196.60
Purchase #5	$150.84	10.667%	$166.9301	$166.93	$166.95	$166.90
Purchase #6	$205.52	5.473%	$216.7681	$216.77	$216.75	$216.80
Purchase #7	$28.39	7.599%	$30.5474	$30.55	$30.55	$30.50
7 purchase totals =	$1,158.69		$1,259.4760	$1,259.48	$1,259.45	$1,259.40