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	$123.32	10.811%	$136.6521	$136.65	$136.65	$136.70
Purchase #2	$207.54	9.158%	$226.5465	$226.55	$226.55	$226.50
Purchase #3	$241.72	10.657%	$267.4801	$267.48	$267.50	$267.50
Purchase #4	$47.88	9.606%	$52.4794	$52.48	$52.50	$52.50
Purchase #5	$64.97	9.863%	$71.378	$71.38	$71.40	$71.40
Purchase #6	$102.51	3.528%	$106.1266	$106.13	$106.15	$106.10
Purchase #7	$144.45	7.725%	$155.6088	$155.61	$155.60	$155.60
7 purchase totals =	$932.39		$1,016.2715	$1,016.28	$1,016.35	$1,016.30