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	$130.30	4.805%	$136.5609	$136.56	$136.55	$136.60
Purchase #2	$225.35	3.711%	$233.7127	$233.71	$233.70	$233.70
Purchase #3	$208.44	4.330%	$217.4655	$217.47	$217.45	$217.50
Purchase #4	$164.41	3.457%	$170.0937	$170.09	$170.10	$170.10
Purchase #5	$102.78	5.607%	$108.5429	$108.54	$108.55	$108.50
Purchase #6	$76.74	7.761%	$82.6958	$82.70	$82.70	$82.70
Purchase #7	$141.37	6.728%	$150.8814	$150.88	$150.90	$150.90
7 purchase totals =	$1,049.39		$1,099.9529	$1,099.95	$1,099.95	$1,100.00