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	$59.81	8.532%	$64.913	$64.91	$64.90	$64.90
Purchase #2	$217.64	5.630%	$229.8931	$229.89	$229.90	$229.90
Purchase #3	$57.27	12.447%	$64.3984	$64.40	$64.40	$64.40
Purchase #4	$102.28	7.482%	$109.9326	$109.93	$109.95	$109.90
Purchase #5	$6.54	5.418%	$6.8943	$6.89	$6.90	$6.90
Purchase #6	$225.58	11.173%	$250.7841	$250.78	$250.80	$250.80
Purchase #7	$177.86	8.235%	$192.5068	$192.51	$192.50	$192.50
7 purchase totals =	$846.98		$919.3223	$919.31	$919.35	$919.30