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	$136.61	4.429%	$142.6605	$142.66	$142.65	$142.70
Purchase #2	$208.52	3.206%	$215.2052	$215.21	$215.20	$215.20
Purchase #3	$196.95	7.847%	$212.4047	$212.40	$212.40	$212.40
Purchase #4	$27.55	4.419%	$28.7674	$28.77	$28.75	$28.80
Purchase #5	$152.70	9.550%	$167.2829	$167.28	$167.30	$167.30
Purchase #6	$100.81	10.621%	$111.517	$111.52	$111.50	$111.50
Purchase #7	$123.92	9.631%	$135.8547	$135.85	$135.85	$135.90
7 purchase totals =	$947.06		$1,013.6924	$1,013.69	$1,013.65	$1,013.80