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	$98.56	5.716%	$104.1937	$104.19	$104.20	$104.20
Purchase #2	$31.39	7.861%	$33.8576	$33.86	$33.85	$33.90
Purchase #3	$11.68	10.460%	$12.9017	$12.90	$12.90	$12.90
Purchase #4	$76.95	5.117%	$80.8875	$80.89	$80.90	$80.90
Purchase #5	$159.92	11.537%	$178.37	$178.37	$178.35	$178.40
Purchase #6	$57.46	9.172%	$62.7302	$62.73	$62.75	$62.70
Purchase #7	$126.82	12.416%	$142.566	$142.57	$142.55	$142.60
7 purchase totals =	$562.78		$615.5067	$615.51	$615.50	$615.60