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	$51.66	6.126%	$54.8247	$54.82	$54.80	$54.80
Purchase #2	$208.98	3.469%	$216.2295	$216.23	$216.25	$216.20
Purchase #3	$166.77	12.407%	$187.4612	$187.46	$187.45	$187.50
Purchase #4	$162.73	5.529%	$171.7273	$171.73	$171.75	$171.70
Purchase #5	$50.35	7.314%	$54.0326	$54.03	$54.05	$54.00
Purchase #6	$171.31	3.116%	$176.648	$176.65	$176.65	$176.60
Purchase #7	$73.93	10.864%	$81.9618	$81.96	$81.95	$82.00
7 purchase totals =	$885.73		$942.8851	$942.88	$942.90	$942.80