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	$50.50	9.102%	$55.0965	$55.10	$55.10	$55.10
Purchase #2	$102.76	7.289%	$110.2502	$110.25	$110.25	$110.30
Purchase #3	$137.57	11.838%	$153.8555	$153.86	$153.85	$153.90
Purchase #4	$183.66	4.302%	$191.5611	$191.56	$191.55	$191.60
Purchase #5	$209.75	8.168%	$226.8824	$226.88	$226.90	$226.90
Purchase #6	$244.48	4.500%	$255.4816	$255.48	$255.50	$255.50
Purchase #7	$114.82	7.499%	$123.4304	$123.43	$123.45	$123.40
7 purchase totals =	$1,043.54		$1,116.5577	$1,116.56	$1,116.60	$1,116.70