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	$206.94	12.658%	$233.1345	$233.13	$233.15	$233.10
Purchase #2	$96.89	9.183%	$105.7874	$105.79	$105.80	$105.80
Purchase #3	$81.26	3.218%	$83.8749	$83.87	$83.85	$83.90
Purchase #4	$164.64	8.183%	$178.1125	$178.11	$178.10	$178.10
Purchase #5	$242.99	12.509%	$273.3856	$273.39	$273.40	$273.40
Purchase #6	$80.93	10.712%	$89.5992	$89.60	$89.60	$89.60
Purchase #7	$219.92	4.224%	$229.2094	$229.21	$229.20	$229.20
7 purchase totals =	$1,093.57		$1,193.1035	$1,193.10	$1,193.10	$1,193.10