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	$96.52	9.437%	$105.6286	$105.63	$105.65	$105.60
Purchase #2	$50.26	7.659%	$54.1094	$54.11	$54.10	$54.10
Purchase #3	$36.95	5.505%	$38.9841	$38.98	$39.00	$39.00
Purchase #4	$97.83	13.585%	$111.1202	$111.12	$111.10	$111.10
Purchase #5	$208.31	6.838%	$222.5542	$222.55	$222.55	$222.60
Purchase #6	$21.64	4.870%	$22.6939	$22.69	$22.70	$22.70
Purchase #7	$171.29	6.386%	$182.2286	$182.23	$182.25	$182.20
7 purchase totals =	$682.80		$737.3190	$737.31	$737.35	$737.30