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	$243.80	7.442%	$261.9436	$261.94	$261.95	$261.90
Purchase #2	$214.32	4.509%	$223.9837	$223.98	$224.00	$224.00
Purchase #3	$183.72	7.185%	$196.9203	$196.92	$196.90	$196.90
Purchase #4	$221.86	7.553%	$238.6171	$238.62	$238.60	$238.60
Purchase #5	$189.63	8.517%	$205.7808	$205.78	$205.80	$205.80
Purchase #6	$88.42	9.259%	$96.6068	$96.61	$96.60	$96.60
Purchase #7	$130.62	11.862%	$146.1141	$146.11	$146.10	$146.10
7 purchase totals =	$1,272.37		$1,369.9664	$1,369.96	$1,369.95	$1,369.90