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	$92.60	13.349%	$104.9612	$104.96	$104.95	$105.00
Purchase #2	$88.81	9.393%	$97.1519	$97.15	$97.15	$97.20
Purchase #3	$87.59	10.503%	$96.7896	$96.79	$96.80	$96.80
Purchase #4	$45.90	12.296%	$51.5439	$51.54	$51.55	$51.50
Purchase #5	$82.55	3.375%	$85.3361	$85.34	$85.35	$85.30
Purchase #6	$141.82	9.193%	$154.8575	$154.86	$154.85	$154.90
Purchase #7	$161.45	4.656%	$168.9671	$168.97	$168.95	$169.00
7 purchase totals =	$700.72		$759.6073	$759.61	$759.60	$759.70