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	$200.25	8.606%	$217.4835	$217.48	$217.50	$217.50
Purchase #2	$72.76	10.442%	$80.3576	$80.36	$80.35	$80.40
Purchase #3	$33.46	11.122%	$37.1814	$37.18	$37.20	$37.20
Purchase #4	$239.81	12.622%	$270.0788	$270.08	$270.10	$270.10
Purchase #5	$154.90	6.457%	$164.9019	$164.90	$164.90	$164.90
Purchase #6	$224.31	10.632%	$248.1586	$248.16	$248.15	$248.20
Purchase #7	$163.85	11.261%	$182.3011	$182.30	$182.30	$182.30
7 purchase totals =	$1,089.34		$1,200.4629	$1,200.46	$1,200.50	$1,200.60