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	$72.71	7.652%	$78.2738	$78.27	$78.25	$78.30
Purchase #2	$167.30	5.359%	$176.2656	$176.27	$176.25	$176.30
Purchase #3	$196.80	7.653%	$211.8611	$211.86	$211.85	$211.90
Purchase #4	$13.67	5.233%	$14.3854	$14.39	$14.40	$14.40
Purchase #5	$51.62	4.551%	$53.9692	$53.97	$53.95	$54.00
Purchase #6	$152.87	13.530%	$173.5533	$173.55	$173.55	$173.60
Purchase #7	$30.47	5.269%	$32.0755	$32.08	$32.10	$32.10
7 purchase totals =	$685.44		$740.3839	$740.39	$740.35	$740.60