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	$210.89	9.450%	$230.8191	$230.82	$230.80	$230.80
Purchase #2	$84.91	5.862%	$89.8874	$89.89	$89.90	$89.90
Purchase #3	$63.92	5.600%	$67.4995	$67.50	$67.50	$67.50
Purchase #4	$156.34	3.747%	$162.1981	$162.20	$162.20	$162.20
Purchase #5	$152.74	9.256%	$166.8776	$166.88	$166.90	$166.90
Purchase #6	$205.48	4.870%	$215.4869	$215.49	$215.50	$215.50
Purchase #7	$158.30	9.151%	$172.786	$172.79	$172.80	$172.80
7 purchase totals =	$1,032.58		$1,105.5546	$1,105.57	$1,105.60	$1,105.60