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	$35.50	8.873%	$38.6499	$38.65	$38.65	$38.60
Purchase #2	$201.57	4.620%	$210.8825	$210.88	$210.90	$210.90
Purchase #3	$114.78	7.502%	$123.3908	$123.39	$123.40	$123.40
Purchase #4	$226.32	6.493%	$241.015	$241.02	$241.00	$241.00
Purchase #5	$156.69	8.695%	$170.3142	$170.31	$170.30	$170.30
Purchase #6	$43.82	5.238%	$46.1153	$46.12	$46.10	$46.10
Purchase #7	$112.48	9.821%	$123.5267	$123.53	$123.55	$123.50
7 purchase totals =	$891.16		$953.8944	$953.90	$953.90	$953.80