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	$41.86	3.166%	$43.1853	$43.19	$43.20	$43.20
Purchase #2	$114.50	11.184%	$127.3057	$127.31	$127.30	$127.30
Purchase #3	$88.49	11.250%	$98.4451	$98.45	$98.45	$98.40
Purchase #4	$126.28	5.641%	$133.4035	$133.40	$133.40	$133.40
Purchase #5	$161.51	4.401%	$168.6181	$168.62	$168.60	$168.60
Purchase #6	$33.38	4.258%	$34.8013	$34.80	$34.80	$34.80
Purchase #7	$102.89	6.526%	$109.6046	$109.60	$109.60	$109.60
7 purchase totals =	$668.91		$715.3636	$715.37	$715.35	$715.30