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	$134.85	5.850%	$142.7387	$142.74	$142.75	$142.70
Purchase #2	$130.98	10.646%	$144.9241	$144.92	$144.90	$144.90
Purchase #3	$26.88	3.521%	$27.8264	$27.83	$27.85	$27.80
Purchase #4	$66.60	11.563%	$74.301	$74.30	$74.30	$74.30
Purchase #5	$100.72	11.746%	$112.5506	$112.55	$112.55	$112.60
Purchase #6	$67.34	7.229%	$72.208	$72.21	$72.20	$72.20
Purchase #7	$89.29	9.692%	$97.944	$97.94	$97.95	$97.90
7 purchase totals =	$616.66		$672.4928	$672.49	$672.50	$672.40