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	$217.25	4.422%	$226.8568	$226.86	$226.85	$226.90
Purchase #2	$84.82	3.542%	$87.8243	$87.82	$87.80	$87.80
Purchase #3	$32.45	4.510%	$33.9135	$33.91	$33.90	$33.90
Purchase #4	$102.91	3.111%	$106.1115	$106.11	$106.10	$106.10
Purchase #5	$99.45	13.469%	$112.8449	$112.84	$112.85	$112.80
Purchase #6	$105.31	10.459%	$116.3244	$116.32	$116.30	$116.30
Purchase #7	$164.65	4.184%	$171.539	$171.54	$171.55	$171.50
7 purchase totals =	$806.84		$855.4144	$855.40	$855.35	$855.30