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	$182.43	9.699%	$200.1239	$200.12	$200.10	$200.10
Purchase #2	$208.99	9.786%	$229.4418	$229.44	$229.45	$229.40
Purchase #3	$153.50	4.549%	$160.4827	$160.48	$160.50	$160.50
Purchase #4	$21.64	12.817%	$24.4136	$24.41	$24.40	$24.40
Purchase #5	$56.70	5.731%	$59.9495	$59.95	$59.95	$59.90
Purchase #6	$127.33	11.634%	$142.1436	$142.14	$142.15	$142.10
Purchase #7	$62.94	6.474%	$67.0147	$67.01	$67.00	$67.00
7 purchase totals =	$813.53		$883.5698	$883.55	$883.55	$883.40