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	$157.26	13.833%	$179.0138	$179.01	$179.00	$179.00
Purchase #2	$65.90	10.419%	$72.7661	$72.77	$72.75	$72.80
Purchase #3	$83.82	12.607%	$94.3872	$94.39	$94.40	$94.40
Purchase #4	$187.28	5.741%	$198.0317	$198.03	$198.05	$198.00
Purchase #5	$54.30	9.697%	$59.5655	$59.57	$59.55	$59.60
Purchase #6	$50.50	10.595%	$55.8505	$55.85	$55.85	$55.90
Purchase #7	$56.29	10.812%	$62.3761	$62.38	$62.40	$62.40
7 purchase totals =	$655.35		$721.9909	$722.00	$722.00	$722.10