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	$140.63	6.677%	$150.0199	$150.02	$150.00	$150.00
Purchase #2	$62.40	10.594%	$69.0107	$69.01	$69.00	$69.00
Purchase #3	$214.33	6.634%	$228.5487	$228.55	$228.55	$228.50
Purchase #4	$87.68	8.251%	$94.9145	$94.91	$94.90	$94.90
Purchase #5	$196.83	11.105%	$218.688	$218.69	$218.70	$218.70
Purchase #6	$147.56	11.670%	$164.7803	$164.78	$164.80	$164.80
Purchase #7	$131.33	4.602%	$137.3738	$137.37	$137.35	$137.40
7 purchase totals =	$980.76		$1,063.3359	$1,063.33	$1,063.30	$1,063.30