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	$57.85	13.411%	$65.6083	$65.61	$65.60	$65.60
Purchase #2	$91.85	7.133%	$98.4017	$98.40	$98.40	$98.40
Purchase #3	$146.95	3.612%	$152.2578	$152.26	$152.25	$152.30
Purchase #4	$163.25	4.871%	$171.2019	$171.20	$171.20	$171.20
Purchase #5	$212.31	8.136%	$229.5835	$229.58	$229.60	$229.60
Purchase #6	$67.25	13.748%	$76.4955	$76.50	$76.50	$76.50
Purchase #7	$82.88	4.502%	$86.6113	$86.61	$86.60	$86.60
7 purchase totals =	$822.34		$880.1600	$880.16	$880.15	$880.20