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	$210.67	9.400%	$230.473	$230.47	$230.45	$230.50
Purchase #2	$156.69	6.661%	$167.1271	$167.13	$167.15	$167.10
Purchase #3	$78.27	8.679%	$85.0631	$85.06	$85.05	$85.10
Purchase #4	$177.57	10.193%	$195.6697	$195.67	$195.65	$195.70
Purchase #5	$156.30	3.817%	$162.266	$162.27	$162.25	$162.30
Purchase #6	$216.71	10.798%	$240.1103	$240.11	$240.10	$240.10
Purchase #7	$42.64	8.746%	$46.3693	$46.37	$46.35	$46.40
7 purchase totals =	$1,038.85		$1,127.0785	$1,127.08	$1,127.00	$1,127.20