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	$173.52	5.374%	$182.845	$182.85	$182.85	$182.80
Purchase #2	$39.29	12.517%	$44.2079	$44.21	$44.20	$44.20
Purchase #3	$156.65	4.861%	$164.2648	$164.26	$164.25	$164.30
Purchase #4	$18.27	12.211%	$20.5009	$20.50	$20.50	$20.50
Purchase #5	$233.30	3.274%	$240.9382	$240.94	$240.95	$240.90
Purchase #6	$135.64	10.777%	$150.2579	$150.26	$150.25	$150.30
Purchase #7	$186.74	6.296%	$198.4972	$198.50	$198.50	$198.50
7 purchase totals =	$943.41		$1,001.5119	$1,001.52	$1,001.50	$1,001.50