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	$100.88	13.558%	$114.5573	$114.56	$114.55	$114.60
Purchase #2	$142.85	13.478%	$162.1033	$162.10	$162.10	$162.10
Purchase #3	$182.86	12.207%	$205.1817	$205.18	$205.20	$205.20
Purchase #4	$18.98	8.380%	$20.5705	$20.57	$20.55	$20.60
Purchase #5	$60.84	11.359%	$67.7508	$67.75	$67.75	$67.80
Purchase #6	$30.41	10.824%	$33.7016	$33.70	$33.70	$33.70
Purchase #7	$11.46	9.132%	$12.5065	$12.51	$12.50	$12.50
7 purchase totals =	$548.28		$616.3717	$616.37	$616.35	$616.50