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	$57.83	13.614%	$65.703	$65.70	$65.70	$65.70
Purchase #2	$151.36	7.280%	$162.379	$162.38	$162.40	$162.40
Purchase #3	$153.44	4.249%	$159.9597	$159.96	$159.95	$160.00
Purchase #4	$242.43	13.417%	$274.9568	$274.96	$274.95	$275.00
Purchase #5	$153.93	5.796%	$162.8518	$162.85	$162.85	$162.90
Purchase #6	$43.33	5.775%	$45.8323	$45.83	$45.85	$45.80
Purchase #7	$190.45	11.108%	$211.6052	$211.61	$211.60	$211.60
7 purchase totals =	$992.77		$1,083.2878	$1,083.29	$1,083.30	$1,083.40