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	$168.30	10.122%	$185.3353	$185.34	$185.35	$185.30
Purchase #2	$56.69	9.123%	$61.8618	$61.86	$61.85	$61.90
Purchase #3	$65.79	10.699%	$72.8289	$72.83	$72.85	$72.80
Purchase #4	$119.40	6.644%	$127.3329	$127.33	$127.35	$127.30
Purchase #5	$163.46	13.550%	$185.6088	$185.61	$185.60	$185.60
Purchase #6	$176.40	11.744%	$197.1164	$197.12	$197.10	$197.10
Purchase #7	$116.93	8.476%	$126.841	$126.84	$126.85	$126.80
7 purchase totals =	$866.97		$956.9251	$956.93	$956.95	$956.80