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	$107.25	11.195%	$119.2566	$119.26	$119.25	$119.30
Purchase #2	$216.75	12.375%	$243.5728	$243.57	$243.55	$243.60
Purchase #3	$132.72	11.869%	$148.4725	$148.47	$148.45	$148.50
Purchase #4	$166.34	9.377%	$181.9377	$181.94	$181.95	$181.90
Purchase #5	$75.26	8.663%	$81.7798	$81.78	$81.80	$81.80
Purchase #6	$103.88	4.254%	$108.2991	$108.30	$108.30	$108.30
Purchase #7	$162.89	3.424%	$168.4674	$168.47	$168.45	$168.50
7 purchase totals =	$965.09		$1,051.7859	$1,051.79	$1,051.75	$1,051.90