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	$188.32	9.442%	$206.1012	$206.10	$206.10	$206.10
Purchase #2	$49.31	8.239%	$53.3727	$53.37	$53.35	$53.40
Purchase #3	$133.62	13.156%	$151.199	$151.20	$151.20	$151.20
Purchase #4	$27.32	4.299%	$28.4945	$28.49	$28.50	$28.50
Purchase #5	$153.90	9.108%	$167.9172	$167.92	$167.90	$167.90
Purchase #6	$92.56	8.534%	$100.4591	$100.46	$100.45	$100.50
Purchase #7	$156.65	9.694%	$171.8357	$171.84	$171.85	$171.80
7 purchase totals =	$801.68		$879.3794	$879.38	$879.35	$879.40