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	$46.60	9.478%	$51.0167	$51.02	$51.00	$51.00
Purchase #2	$50.46	13.393%	$57.2181	$57.22	$57.20	$57.20
Purchase #3	$183.53	7.193%	$196.7313	$196.73	$196.75	$196.70
Purchase #4	$239.91	6.342%	$255.1251	$255.13	$255.15	$255.10
Purchase #5	$71.76	13.357%	$81.345	$81.35	$81.35	$81.30
Purchase #6	$131.66	9.664%	$144.3836	$144.38	$144.40	$144.40
Purchase #7	$89.32	9.747%	$98.026	$98.03	$98.05	$98.00
7 purchase totals =	$813.24		$883.8458	$883.86	$883.90	$883.70