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	$238.32	13.546%	$270.6028	$270.60	$270.60	$270.60
Purchase #2	$228.52	4.202%	$238.1224	$238.12	$238.10	$238.10
Purchase #3	$11.83	4.378%	$12.3479	$12.35	$12.35	$12.30
Purchase #4	$60.42	6.834%	$64.5491	$64.55	$64.55	$64.50
Purchase #5	$147.90	13.838%	$168.3664	$168.37	$168.35	$168.40
Purchase #6	$152.38	12.803%	$171.8892	$171.89	$171.90	$171.90
Purchase #7	$208.96	8.178%	$226.0487	$226.05	$226.05	$226.00
7 purchase totals =	$1,048.33		$1,151.9265	$1,151.93	$1,151.90	$1,151.80