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	$171.92	3.259%	$177.5229	$177.52	$177.50	$177.50
Purchase #2	$101.85	4.387%	$106.3182	$106.32	$106.30	$106.30
Purchase #3	$55.83	6.175%	$59.2775	$59.28	$59.30	$59.30
Purchase #4	$51.79	6.115%	$54.957	$54.96	$54.95	$55.00
Purchase #5	$67.97	6.477%	$72.3724	$72.37	$72.35	$72.40
Purchase #6	$62.73	11.467%	$69.9232	$69.92	$69.90	$69.90
Purchase #7	$126.55	5.851%	$133.9544	$133.95	$133.95	$134.00
7 purchase totals =	$638.64		$674.3256	$674.32	$674.25	$674.40