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	$167.66	10.470%	$185.214	$185.21	$185.20	$185.20
Purchase #2	$162.50	3.717%	$168.5401	$168.54	$168.55	$168.50
Purchase #3	$199.30	7.462%	$214.1718	$214.17	$214.15	$214.20
Purchase #4	$8.43	13.493%	$9.5675	$9.57	$9.55	$9.60
Purchase #5	$158.64	3.624%	$164.3891	$164.39	$164.40	$164.40
Purchase #6	$189.92	3.521%	$196.6071	$196.61	$196.60	$196.60
Purchase #7	$75.96	13.571%	$86.2685	$86.27	$86.25	$86.30
7 purchase totals =	$962.41		$1,024.7581	$1,024.76	$1,024.70	$1,024.80