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	$114.32	11.411%	$127.3651	$127.37	$127.35	$127.40
Purchase #2	$143.95	11.609%	$160.6612	$160.66	$160.65	$160.70
Purchase #3	$168.60	7.562%	$181.3495	$181.35	$181.35	$181.30
Purchase #4	$83.38	8.426%	$90.4056	$90.41	$90.40	$90.40
Purchase #5	$201.65	4.823%	$211.3756	$211.38	$211.40	$211.40
Purchase #6	$130.53	11.523%	$145.571	$145.57	$145.55	$145.60
Purchase #7	$167.83	10.147%	$184.8597	$184.86	$184.85	$184.90
7 purchase totals =	$1,010.26		$1,101.5877	$1,101.60	$1,101.55	$1,101.70