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	$63.97	9.749%	$70.2064	$70.21	$70.20	$70.20
Purchase #2	$131.89	5.513%	$139.1611	$139.16	$139.15	$139.20
Purchase #3	$170.67	6.652%	$182.023	$182.02	$182.00	$182.00
Purchase #4	$57.91	9.262%	$63.2736	$63.27	$63.25	$63.30
Purchase #5	$101.54	7.801%	$109.4611	$109.46	$109.45	$109.50
Purchase #6	$54.73	4.770%	$57.3406	$57.34	$57.35	$57.30
Purchase #7	$141.73	8.317%	$153.5177	$153.52	$153.50	$153.50
7 purchase totals =	$722.44		$774.9835	$774.98	$774.90	$775.00