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	$198.52	9.545%	$217.4687	$217.47	$217.45	$217.50
Purchase #2	$68.33	7.799%	$73.6591	$73.66	$73.65	$73.70
Purchase #3	$86.76	12.404%	$97.5217	$97.52	$97.50	$97.50
Purchase #4	$85.79	5.430%	$90.4484	$90.45	$90.45	$90.40
Purchase #5	$158.50	6.443%	$168.7122	$168.71	$168.70	$168.70
Purchase #6	$161.44	8.287%	$174.8185	$174.82	$174.80	$174.80
Purchase #7	$83.50	8.834%	$90.8764	$90.88	$90.90	$90.90
7 purchase totals =	$842.84		$913.5050	$913.51	$913.45	$913.50