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	$41.40	4.668%	$43.3326	$43.33	$43.35	$43.30
Purchase #2	$226.93	12.540%	$255.387	$255.39	$255.40	$255.40
Purchase #3	$196.26	9.337%	$214.5848	$214.58	$214.60	$214.60
Purchase #4	$154.90	7.835%	$167.0364	$167.04	$167.05	$167.00
Purchase #5	$242.65	4.870%	$254.4671	$254.47	$254.45	$254.50
Purchase #6	$16.99	7.196%	$18.2126	$18.21	$18.20	$18.20
Purchase #7	$98.59	9.600%	$108.0546	$108.05	$108.05	$108.10
7 purchase totals =	$977.72		$1,061.0751	$1,061.07	$1,061.10	$1,061.10