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	$43.63	4.854%	$45.7478	$45.75	$45.75	$45.70
Purchase #2	$98.39	11.204%	$109.4136	$109.41	$109.40	$109.40
Purchase #3	$45.64	13.561%	$51.8292	$51.83	$51.85	$51.80
Purchase #4	$142.31	5.740%	$150.4786	$150.48	$150.50	$150.50
Purchase #5	$174.44	10.584%	$192.9027	$192.90	$192.90	$192.90
Purchase #6	$103.43	10.433%	$114.2209	$114.22	$114.20	$114.20
Purchase #7	$215.90	5.242%	$227.2175	$227.22	$227.20	$227.20
7 purchase totals =	$823.74		$891.8103	$891.81	$891.80	$891.70