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	$57.58	7.669%	$61.9958	$62.00	$62.00	$62.00
Purchase #2	$57.40	13.537%	$65.1702	$65.17	$65.15	$65.20
Purchase #3	$228.46	11.836%	$255.5005	$255.50	$255.50	$255.50
Purchase #4	$227.37	11.864%	$254.3452	$254.35	$254.35	$254.30
Purchase #5	$226.30	9.571%	$247.9592	$247.96	$247.95	$248.00
Purchase #6	$158.83	6.109%	$168.5329	$168.53	$168.55	$168.50
Purchase #7	$147.58	9.648%	$161.8185	$161.82	$161.80	$161.80
7 purchase totals =	$1,103.52		$1,215.3223	$1,215.33	$1,215.30	$1,215.30