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	$43.59	6.685%	$46.504	$46.50	$46.50	$46.50
Purchase #2	$136.52	5.810%	$144.4518	$144.45	$144.45	$144.50
Purchase #3	$58.70	5.684%	$62.0365	$62.04	$62.05	$62.00
Purchase #4	$60.39	4.172%	$62.9095	$62.91	$62.90	$62.90
Purchase #5	$65.38	12.713%	$73.6918	$73.69	$73.70	$73.70
Purchase #6	$172.81	4.795%	$181.0962	$181.10	$181.10	$181.10
Purchase #7	$232.46	9.367%	$254.2345	$254.23	$254.25	$254.20
7 purchase totals =	$769.85		$824.9243	$824.92	$824.95	$824.90