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	$96.31	13.256%	$109.0769	$109.08	$109.10	$109.10
Purchase #2	$180.38	6.356%	$191.845	$191.85	$191.85	$191.80
Purchase #3	$210.34	13.210%	$238.1259	$238.13	$238.15	$238.10
Purchase #4	$237.32	10.489%	$262.2125	$262.21	$262.20	$262.20
Purchase #5	$156.32	3.682%	$162.0757	$162.08	$162.10	$162.10
Purchase #6	$51.58	10.295%	$56.8902	$56.89	$56.90	$56.90
Purchase #7	$178.90	4.353%	$186.6875	$186.69	$186.70	$186.70
7 purchase totals =	$1,111.15		$1,206.9137	$1,206.93	$1,207.00	$1,206.90