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	$119.98	11.789%	$134.1244	$134.12	$134.10	$134.10
Purchase #2	$115.61	9.853%	$127.0011	$127.00	$127.00	$127.00
Purchase #3	$22.54	11.315%	$25.0904	$25.09	$25.10	$25.10
Purchase #4	$33.47	5.840%	$35.4246	$35.42	$35.40	$35.40
Purchase #5	$7.56	4.320%	$7.8866	$7.89	$7.90	$7.90
Purchase #6	$188.72	8.408%	$204.5876	$204.59	$204.60	$204.60
Purchase #7	$80.44	12.315%	$90.3462	$90.35	$90.35	$90.30
7 purchase totals =	$568.32		$624.4609	$624.46	$624.45	$624.40