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	$126.37	3.659%	$130.9939	$130.99	$131.00	$131.00
Purchase #2	$127.65	11.342%	$142.1281	$142.13	$142.15	$142.10
Purchase #3	$142.70	5.540%	$150.6056	$150.61	$150.60	$150.60
Purchase #4	$110.63	11.669%	$123.5394	$123.54	$123.55	$123.50
Purchase #5	$32.53	9.868%	$35.7401	$35.74	$35.75	$35.70
Purchase #6	$36.79	12.479%	$41.381	$41.38	$41.40	$41.40
Purchase #7	$152.54	12.835%	$172.1185	$172.12	$172.10	$172.10
7 purchase totals =	$729.21		$796.5066	$796.51	$796.55	$796.40