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	$172.45	3.466%	$178.4271	$178.43	$178.45	$178.40
Purchase #2	$151.37	12.684%	$170.5698	$170.57	$170.55	$170.60
Purchase #3	$151.67	11.695%	$169.4078	$169.41	$169.40	$169.40
Purchase #4	$179.67	9.523%	$196.78	$196.78	$196.80	$196.80
Purchase #5	$80.91	5.541%	$85.3932	$85.39	$85.40	$85.40
Purchase #6	$64.84	10.772%	$71.8246	$71.82	$71.80	$71.80
Purchase #7	$217.91	10.813%	$241.4726	$241.47	$241.45	$241.50
7 purchase totals =	$1,018.82		$1,113.8751	$1,113.87	$1,113.85	$1,113.90