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	$48.67	9.225%	$53.1598	$53.16	$53.15	$53.20
Purchase #2	$176.75	11.141%	$196.4417	$196.44	$196.45	$196.40
Purchase #3	$80.72	3.618%	$83.6404	$83.64	$83.65	$83.60
Purchase #4	$76.94	7.383%	$82.6205	$82.62	$82.60	$82.60
Purchase #5	$169.91	5.649%	$179.5082	$179.51	$179.50	$179.50
Purchase #6	$194.32	3.414%	$200.9541	$200.95	$200.95	$201.00
Purchase #7	$91.50	6.103%	$97.0842	$97.08	$97.10	$97.10
7 purchase totals =	$838.81		$893.4089	$893.40	$893.40	$893.40