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	$185.54	6.143%	$196.9377	$196.94	$196.95	$196.90
Purchase #2	$123.48	3.320%	$127.5795	$127.58	$127.60	$127.60
Purchase #3	$197.32	8.402%	$213.8988	$213.90	$213.90	$213.90
Purchase #4	$18.76	11.553%	$20.9273	$20.93	$20.95	$20.90
Purchase #5	$52.66	4.313%	$54.9312	$54.93	$54.95	$54.90
Purchase #6	$173.50	10.719%	$192.0975	$192.10	$192.10	$192.10
Purchase #7	$122.92	5.645%	$129.8588	$129.86	$129.85	$129.90
7 purchase totals =	$874.18		$936.2308	$936.24	$936.30	$936.20