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	$154.83	12.343%	$173.9407	$173.94	$173.95	$173.90
Purchase #2	$118.78	7.136%	$127.2561	$127.26	$127.25	$127.30
Purchase #3	$219.62	10.594%	$242.8865	$242.89	$242.90	$242.90
Purchase #4	$140.46	8.649%	$152.6084	$152.61	$152.60	$152.60
Purchase #5	$158.76	5.309%	$167.1886	$167.19	$167.20	$167.20
Purchase #6	$24.46	10.432%	$27.0117	$27.01	$27.00	$27.00
Purchase #7	$130.48	3.527%	$135.082	$135.08	$135.10	$135.10
7 purchase totals =	$947.39		$1,025.9740	$1,025.98	$1,026.00	$1,026.00