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	$102.80	8.867%	$111.9153	$111.92	$111.90	$111.90
Purchase #2	$11.96	9.434%	$13.0883	$13.09	$13.10	$13.10
Purchase #3	$183.88	5.825%	$194.591	$194.59	$194.60	$194.60
Purchase #4	$140.48	11.430%	$156.5369	$156.54	$156.55	$156.50
Purchase #5	$80.48	7.196%	$86.2713	$86.27	$86.25	$86.30
Purchase #6	$233.39	13.714%	$265.3971	$265.40	$265.40	$265.40
Purchase #7	$72.76	8.274%	$78.7802	$78.78	$78.80	$78.80
7 purchase totals =	$825.75		$906.5801	$906.59	$906.60	$906.60