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	$142.98	9.532%	$156.6089	$156.61	$156.60	$156.60
Purchase #2	$118.25	12.525%	$133.0608	$133.06	$133.05	$133.10
Purchase #3	$164.54	7.337%	$176.6123	$176.61	$176.60	$176.60
Purchase #4	$170.98	8.693%	$185.8433	$185.84	$185.85	$185.80
Purchase #5	$223.89	5.561%	$236.3405	$236.34	$236.35	$236.30
Purchase #6	$53.97	11.743%	$60.3077	$60.31	$60.30	$60.30
Purchase #7	$81.68	10.500%	$90.2564	$90.26	$90.25	$90.30
7 purchase totals =	$956.29		$1,039.0299	$1,039.03	$1,039.00	$1,039.00