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	$149.97	12.251%	$168.3428	$168.34	$168.35	$168.30
Purchase #2	$157.87	13.701%	$179.4998	$179.50	$179.50	$179.50
Purchase #3	$185.58	3.788%	$192.6098	$192.61	$192.60	$192.60
Purchase #4	$96.86	7.228%	$103.861	$103.86	$103.85	$103.90
Purchase #5	$48.64	9.362%	$53.1937	$53.19	$53.20	$53.20
Purchase #6	$192.52	10.688%	$213.0965	$213.10	$213.10	$213.10
Purchase #7	$125.54	10.799%	$139.0971	$139.10	$139.10	$139.10
7 purchase totals =	$956.98		$1,049.7007	$1,049.70	$1,049.70	$1,049.70