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	$96.25	13.342%	$109.0917	$109.09	$109.10	$109.10
Purchase #2	$216.58	12.440%	$243.5226	$243.52	$243.50	$243.50
Purchase #3	$213.35	6.865%	$227.9965	$228.00	$228.00	$228.00
Purchase #4	$121.56	5.754%	$128.5546	$128.55	$128.55	$128.60
Purchase #5	$47.94	10.242%	$52.85	$52.85	$52.85	$52.90
Purchase #6	$119.37	10.223%	$131.5732	$131.57	$131.55	$131.60
Purchase #7	$239.78	8.339%	$259.7753	$259.78	$259.80	$259.80
7 purchase totals =	$1,054.83		$1,153.3639	$1,153.36	$1,153.35	$1,153.50