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	$86.95	6.336%	$92.4592	$92.46	$92.45	$92.50
Purchase #2	$124.28	10.673%	$137.5444	$137.54	$137.55	$137.50
Purchase #3	$36.50	5.392%	$38.4681	$38.47	$38.45	$38.50
Purchase #4	$246.95	9.462%	$270.3164	$270.32	$270.30	$270.30
Purchase #5	$151.66	8.430%	$164.4449	$164.44	$164.45	$164.40
Purchase #6	$125.33	4.525%	$131.0012	$131.00	$131.00	$131.00
Purchase #7	$130.40	12.825%	$147.1238	$147.12	$147.10	$147.10
7 purchase totals =	$902.07		$981.3580	$981.35	$981.30	$981.30