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	$49.31	6.596%	$52.5625	$52.56	$52.55	$52.60
Purchase #2	$28.46	3.468%	$29.447	$29.45	$29.45	$29.40
Purchase #3	$115.98	9.591%	$127.1036	$127.10	$127.10	$127.10
Purchase #4	$232.47	3.796%	$241.2946	$241.29	$241.30	$241.30
Purchase #5	$134.29	7.676%	$144.5981	$144.60	$144.60	$144.60
Purchase #6	$78.93	7.180%	$84.5972	$84.60	$84.60	$84.60
Purchase #7	$80.52	4.200%	$83.9018	$83.90	$83.90	$83.90
7 purchase totals =	$719.96		$763.5048	$763.50	$763.50	$763.50