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	$193.76	3.455%	$200.4544	$200.45	$200.45	$200.50
Purchase #2	$51.74	12.345%	$58.1273	$58.13	$58.15	$58.10
Purchase #3	$10.34	4.284%	$10.783	$10.78	$10.80	$10.80
Purchase #4	$48.98	5.166%	$51.5103	$51.51	$51.50	$51.50
Purchase #5	$138.28	13.725%	$157.2589	$157.26	$157.25	$157.30
Purchase #6	$6.55	12.443%	$7.365	$7.37	$7.35	$7.40
Purchase #7	$51.79	5.771%	$54.7788	$54.78	$54.80	$54.80
7 purchase totals =	$501.44		$540.2777	$540.28	$540.30	$540.40