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	$78.74	11.343%	$87.6715	$87.67	$87.65	$87.70
Purchase #2	$123.62	6.677%	$131.8741	$131.87	$131.85	$131.90
Purchase #3	$52.64	13.175%	$59.5753	$59.58	$59.60	$59.60
Purchase #4	$195.92	9.176%	$213.8976	$213.90	$213.90	$213.90
Purchase #5	$157.35	7.230%	$168.7264	$168.73	$168.75	$168.70
Purchase #6	$242.54	7.615%	$261.0094	$261.01	$261.00	$261.00
Purchase #7	$85.61	12.392%	$96.2188	$96.22	$96.20	$96.20
7 purchase totals =	$936.42		$1,018.9731	$1,018.98	$1,018.95	$1,019.00