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	$221.73	11.573%	$247.3908	$247.39	$247.40	$247.40
Purchase #2	$125.86	4.479%	$131.4973	$131.50	$131.50	$131.50
Purchase #3	$146.39	10.278%	$161.436	$161.44	$161.45	$161.40
Purchase #4	$176.66	13.431%	$200.3872	$200.39	$200.40	$200.40
Purchase #5	$224.96	11.314%	$250.412	$250.41	$250.40	$250.40
Purchase #6	$42.87	10.167%	$47.2286	$47.23	$47.25	$47.20
Purchase #7	$128.89	11.749%	$144.0333	$144.03	$144.05	$144.00
7 purchase totals =	$1,067.36		$1,182.3852	$1,182.39	$1,182.45	$1,182.30