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	$132.26	13.787%	$150.4947	$150.49	$150.50	$150.50
Purchase #2	$162.25	12.526%	$182.5734	$182.57	$182.55	$182.60
Purchase #3	$170.82	11.613%	$190.6573	$190.66	$190.65	$190.70
Purchase #4	$90.88	8.266%	$98.3921	$98.39	$98.40	$98.40
Purchase #5	$105.47	4.747%	$110.4767	$110.48	$110.50	$110.50
Purchase #6	$160.81	7.268%	$172.4977	$172.50	$172.50	$172.50
Purchase #7	$148.36	13.801%	$168.8352	$168.84	$168.85	$168.80
7 purchase totals =	$970.85		$1,073.9271	$1,073.93	$1,073.95	$1,074.00