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	$193.62	5.555%	$204.3756	$204.38	$204.40	$204.40
Purchase #2	$110.31	3.301%	$113.9513	$113.95	$113.95	$114.00
Purchase #3	$185.96	3.741%	$192.9168	$192.92	$192.90	$192.90
Purchase #4	$140.73	13.348%	$159.5146	$159.51	$159.50	$159.50
Purchase #5	$158.81	6.312%	$168.8341	$168.83	$168.85	$168.80
Purchase #6	$127.97	11.238%	$142.3513	$142.35	$142.35	$142.40
Purchase #7	$72.67	9.560%	$79.6173	$79.62	$79.60	$79.60
7 purchase totals =	$990.07		$1,061.5610	$1,061.56	$1,061.55	$1,061.60