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	$54.71	8.473%	$59.3456	$59.35	$59.35	$59.30
Purchase #2	$11.77	7.677%	$12.6736	$12.67	$12.65	$12.70
Purchase #3	$212.80	5.414%	$224.321	$224.32	$224.30	$224.30
Purchase #4	$193.40	3.704%	$200.5635	$200.56	$200.55	$200.60
Purchase #5	$184.32	8.577%	$200.1291	$200.13	$200.15	$200.10
Purchase #6	$83.30	8.487%	$90.3697	$90.37	$90.35	$90.40
Purchase #7	$122.34	13.738%	$139.1471	$139.15	$139.15	$139.10
7 purchase totals =	$862.64		$926.5496	$926.55	$926.50	$926.50