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	$72.68	7.155%	$77.8803	$77.88	$77.90	$77.90
Purchase #2	$16.39	13.513%	$18.6048	$18.60	$18.60	$18.60
Purchase #3	$236.72	8.488%	$256.8128	$256.81	$256.80	$256.80
Purchase #4	$16.40	9.412%	$17.9436	$17.94	$17.95	$17.90
Purchase #5	$140.37	3.260%	$144.9461	$144.95	$144.95	$144.90
Purchase #6	$85.77	4.775%	$89.8655	$89.87	$89.85	$89.90
Purchase #7	$146.50	4.128%	$152.5475	$152.55	$152.55	$152.50
7 purchase totals =	$714.83		$758.6006	$758.60	$758.60	$758.50